The 8-bit home computer from 1975 you've never heard of
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- เผยแพร่เมื่อ 31 พ.ค. 2024
- What we have here is a SWTPC 6800 Computer System from 1975. Looking at the machine, you might not guess that this machine is almost as old as the Altair 8800, only coming out about 10 months later! (And about the same age as me!) There are some fundamental differences with the approach this machine takes versus the Altair and some other neat features. Watch to see what's going on inside this machine.
There will be a few videos on this machine as I'm having an amazing time exploring it, so look for more neat stuff.
Part 1: This part!
Part 2: • Let's try to get the S...
--- Video Links
Mike Douglas's TH-cam Channel with lots of videos on the SWTPC 6800:
/ @deramp5113
South West Technical Products Company:
en.wikipedia.org/wiki/SWTPC
The SS-50 Bus used in this machine:
en.wikipedia.org/wiki/SS-50_bus
Adrian's Digital Basement Merch store:
my-store-c82bd2-2.creator-spr...
Adrian's Digital Basement ][ (Second Channel)
/ @adriansdigitalbasement2
Support the channel on Patreon:
/ adriansdigitalbasement
-- Tools
Deoxit D5:
amzn.to/2VvOKy1
store.caig.com/s.nl/it.A/id.16...
O-Ring Pick Set: (I use these to lift chips off boards)
amzn.to/3a9x54J
Elenco Electronics LP-560 Logic Probe:
amzn.to/2VrT5lW
Hakko FR301 Desoldering Iron:
amzn.to/2ye6xC0
Rigol DS1054Z Four Channel Oscilloscope:
www.rigolna.com/products/digi...
Head Worn Magnifying Goggles / Dual Lens Flip-In Head Magnifier:
amzn.to/3adRbuy
TL866II Plus Chip Tester and EPROM programmer: (The MiniPro)
amzn.to/2wG4tlP
www.aliexpress.com/item/33000...
TS100 Soldering Iron:
amzn.to/2K36dJ5
www.ebay.com/itm/TS100-65W-MI...
EEVBlog 121GW Multimeter:
www.eevblog.com/product/121gw/
DSLogic Basic Logic Analyzer:
amzn.to/2RDSDQw
www.ebay.com/itm/USB-Logic-DS...
Magnetic Screw Holder:
amzn.to/3b8LOhG
www.harborfreight.com/4-inch-...
Universal ZIP sockets: (clones, used on my ZIF-64 test machine)
www.ebay.com/itm/14-16-18-20-...
RetroTink 2X Upconverter: (to hook up something like a C64 to HDMI)
www.retrotink.com/
Plato (Clone) Side Cutters: (order five)
www.ebay.com/itm/1-2-5-10PCS-...
Heat Sinks:
www.aliexpress.com/item/32537...
Little squeezy bottles: (available elsewhere too)
amzn.to/3b8LOOI
--- Links
My GitHub repository:
github.com/misterblack1?tab=r...
Commodore Computer Club / Vancouver, WA - Portland, OR - PDX Commodore Users Group
www.commodorecomputerclub.com/
--- Instructional videos
My video on damage-free chip removal:
• How to remove chips wi...
--- Music
Intro music and other tracks by:
Nathan Divino
@itsnathandivino - วิทยาศาสตร์และเทคโนโลยี
I bought and built one of these SWTPC computers. I even wrote quite a bit of software for it and had it working with the SSB disk drives, a Teletype 43 and later a SWTPC VDU/Keyboard combo which was in some kind of mouleded blue/cream case. I later also interconnected the SWTPC computer to a broadcast teletext receiver which let me save the "pages" to floppy disc. I also made my own S100 cards for memory and interfacing to Motorola exorciser boards. Everything was horribly expensive in those days amd one had to save up just to buy another 1K of memory! I'm pretty sure I still have some of the manuals tucked away somewhere. Sadly, I don't have the SSB DOS software you are are looking out for. Sadly all the hardware got ruined in a flood many years ago. Great memories - many thanks and the best of luck getting it operational. I still have 6800, 6821, MC14411 and 6850 Moiorola chips in anti-static tubes along with some 2102 memor chips (they were really fussy about static!).
So what did you wind up doing with the machine? What were your motivations for putting a so much into it? I
I have a couple of these and have been trying to find someone I ran across in comments previously who claimed to have programmed a pacman like game for it using the GT-6144 graphics board. I have one of those boards and have never been able to find anyone who has one or any programs already done for it.
There should be one in my garage, with a floppy drive. I didn't get any documentation or disks with it.
I worked with Motorola Exorcisor systems in the early to mid '80s. Two 'Metrodata' graphics systems that generated NTSC video for cable TV. Each system had six video cards to generate text. One system also had in interface card to use a SMS disk subsystem to store our program guide for up to a week in advance,
Speaking of the SSB disk drives, I made the wire harnesses for those when I was a high school kid in the family garage, at least for the earlier production runs. How that came about was that my dad worked at the Naval Weapons Center annex in Norco, CA at the time, and worked closely with one of the student interns (Tom K.) who eventually graduated and went on to form his own company along with some other bright young engineers (Signetic Designs) making disk drive systems for 8080 based S-100 systems. My dad continued to to be associated with Tom, maintaining a friendship and interest in what he was doing. This was a garage shop type operation at first, and rather than do the tedious work of assembling wire harnesses for the disk drive system themselves, Tom had me do it for them, supplying a fixture and tools, etc for me to use. Later, SSB started making it's disk drive system 6800-based SS-50 systems, and Tom knew somebody there and somehow I ended up doing their wire harnesses too...
Damn, that was such a long time ago. I'm 62 years old now...
So you're also another who 'never heard of the SS50?'
Oh I realize what this is. It was the first computer I ever used. My high school got one donated to it in early 1980 after a two week computer course that had been taught where students brought in their own PCs (Apple ][s. TRS-80 Model 1, Commodore PETs). The SWTPC I used had 8K of RAM, the cassette interface, a TV/keyboard and "Tiny BASIC" which took about 20 minutes to load from cassette. It was the 6800 that launched my IT career as I spent my free time as a 13/14 year old learning BASIC programming. Our school would then add a TRS-80 Model 1 with floppy drives (which never worked) that same year and a pair of Apple ][+ computers in 1981. I wish I still has for nostalgia purposes if nothing else. Thanks for featuring this.
As a radio amateur as well as a retro computing enthusiast, it gives me great pride that radio amateurs of the '70s were a key demographic of early adopters of kit micro computers. And as an added historical bonus, Motorola was birthed in the 1920s, one of its earliest products being a car radio (not amateur), hence the name "motor" plus "ola" (derived from "Victrola").
It was named Galvin Industries. It was changed to Motorola, because of their car radio. One of the early personal computer companies used the Galvin name, but Motorola sued and won a case that forced them to change their name.
I'm a radio amateur, too and have to remark .. half of them were. The other half was ranting that only vacuum tubes are the way to go and that newfangled junk is the demise of amateur radio as they knew it.
Which it, in a way, was. It changed and later the internet WAS stealing their spotlight of (more or less) free international communication.
But this happened with every innovation, starting with phone communication, then SSB instead of AM, then RTTY, then the digital modes, then digital voice .. and will happen with every upcoming one.
I'm weird in this regard, when I'm in a good mood I'm really excited about new stuff, when I'm down I want everyone to go back to .. whatever decade catches my rose-tinted interest at the time. ;)
The 6800 is one of my favorites. I have two 6800 system units, the AC-30 tape unit, several CT-1024s, the rare PR-40 printer, the ultra rare GT-6144 graphics board and the almost impossible to find joystick. The thing takes up an entire desk and a half when fully set up and the powerup sequence reminds me of a jet with all the switches!
i saw this and instantly thought of you!
@@Arivia1 ditto. I don't understand how tech time traveller does not have more subs. Such a great channel.
I’d never heard of these machines until I was watching through your channel, then suddenly it pops up here too!
@@drwhang subbed because of this comment.
Got the hitachi upgrade?
I worked at a company that used the 6809 variant of this machine in the late 80s. My first day on the job I walk in to find a coworker standing on a rolling chair with a watering can pouring water into the case of one of these. Of course, it was turned ON at the time. After I picked my jaw up off the floor and we were properly introduced, he related that this particular machine had a crack in the motherboard no one could find, so they kept a thin layer of water in the bottom of the case to keep the MB swelled up and the mysterious crack sealed so everything worked. The problem was the water would evaporate, and so it had to be "refilled" when the machine started getting flakey; the plastic standoffs made this possible. This company used the 6809 variant as a central processor for a passel of "remote processors" (an in-house built version of the same machine) that monitored sensors and responded to the central processor via phone lines, hardwired, or radio broadcast. The central processor stored data on a dual tape drive (DEC I believe) and my job was, among other things, to duplicate the central processor function on an Apple 2, and later an IBM PC. I did a few other things for them, including the code for a new kind of remote processor with different sensors. Robin or Don: if you're reading this, look me up. J
No F'n way lol. I can think of about 10 better ways to seal that micro crack than filling the case full of water but hey, I guess it was better than no solution!
Do you remember the Apple 3 and the issues it had of the chips popping partially out of the sockets? Apple actually sent out a tech note that suggested holding the Apple 3 above a hard surface at a distance of approximately 5 feet and dropping it. This would reseat the chips in their sockets... Ah the good ole days...
@@retroatx 5 inches, but yeah. I remember...
Sounds like a joke they did to all the new people like finding the blinker fluid or the board stretcher.
@@fredflintstone9609 I didn't even realize that I typed five feet :-)
I bought and built (kit) 3 of these puppies! The 6800 family of CPU's had one of the best instruction sets around!
For a few years, a gentleman by the name of Michael Holley used to exhibit his SWTPC 6800 at VCF East. He had built the thing back in the 70s, and knew about every little nook and craney of that machine. There's a good chance if you come across online documentation about this system, it might very well have been hosted by him at one point.
Brings back fond memories of when I soldered together my first computer (Netronics Cosmac Elf - RCA 1802 with 256 bytes of ram).
Later built (soldering again) an S100 bus based 8088 system. 32 kb ram and 2 8 inch Shugart drives running CPM. Those were the days.
I look at my iPhone now and smile.
I took a train trip for 1.5 hours to visit a SWTPC shop in the city of Delft, one of the first "computer shops" in the netherlands, I was amazed by the enormous capacitors inside. And yes, they sold fully assembled machines, and also the terminal and some printers. I remember seeing a small cash register printer (40-columns) that was fitted on top of a square metal box.
That was the SWTPC PR40 printer. The Tech Time Traveler channel has a good video on it, along with a video on the SWTPC CT-1024, aka TV Typewriter II, which was probably the terminal you saw.
Long before switchmode units large caps were the only option
Excellent memories! Reminds me of a 3-hour-one-way bike ride me and my brother undertook, just to get to Charlotte NC and see the Apple ][ dealer there. We got in so much trouble for that. Should have left Mom a note.
Never heard of? I was about 12 or 13 years old and was drooling over that computer back in the 70's. At that age and at that time it might as well been a million dollars!
It's imposible to get tired of the "was saved from e-waste and actually given to me" sentence.
Kudos on you for this machine, can't wait to see it running.
As a sophomore in high school, this was the only computer I (with help from my dad) could afford. I built the kit but didn't have a terminal to talk to it. I bought an old klienschmit field teletype at a surplus auction. With the help of a local computer shop I wrote code to convert ascii to 5 bit baudot and used the old teletype for a year until I could buy a used, non working tv teletype....good times.... It was a great experience for a 15 yr old budding engineer!
Somebody loved this, I can tell it was an amateur who did everything themselves and probably learned as they went along. The dry lumpy looking solder re-work along with the Flux being left on the board as well as the lifted and re-worked solder traces are all dead give aways.
Hey, I too once loved me some circuitry to death in the exact manners specified. Young experimenter me from the 70s feels slightly attacked. :P
Good find. Those were neat machines, but the 6809 version was even better.
A SWTPC 6800 was the first computer I had seen in person. The man who owned it used a teletype for I/O. That was probably in late 1975. Thanks for the trip down memory lane.
BTW, RAM chips were VERY sensitive to static electricity in those days. So often new RAM was damaged and so had to be tested as part of installation.
Also, since that is not a switching power supply, any short will most certainly cause smoke and likely cause a trail of destroyed components. Have fun. :-)
We built lots of things from SWTP. We used a number of their small audio amps.
And we called the company Sweet Pea.
So much memories. I have worked as a young trainee then beginner engineer on these machines. Actually only on the SWTPC 6809 as far as SWTPC-branded machines go. It was a very advanced machine with RAM page mapping allowing for up to 768K of RAM on an 8-bit CPU, running a small Unix-like O/S called UniFLEX.
As for the 6800, the French manufacturer Goupil was producing a machine that was very much inspired from this one from '79 on, the Goupil (the blue gen.1 and red gen. 2). Bus-based too, almost a clone actually, but a complete computer with a video controller, keyboard etc. I still remember the ROM monitor commands (was that MICMON?). It ran the FLEX 6800 o/s which was rather advanced for its time, booting from 5.25" or 8" floppies.
IIRC, the Goupil was a team effort, a microcomputer by computing hobbyists for computing hobbyists. It was supposed to be a hacker's dream, designed to meet a hacker's checklist. It was not a corporate product. The most striking thing about it was its built-in acoustic coupler. And the beyond complete keyboard.
Fishing through some old issues of Micro-Systèmes magazine from 1980, only found a handful of full-page adverts towards the end of each issue, never found an actual article about them. It shows they didn't have a corporate budget for marketing.
I was also an apprentice computer tech and cut my teeth on the SWTP! After repairing one of these, I always smiled and gave a little cheer when the '$' symbol appeared on the monitor! Happy days!
This brings back many memories! I assembled several of these for customers while working for a distributor that carried the SWTPC product line back in 1976-79. This computer was designed to be as inexpensive as possible to buy. Using the MIKBUG rom monitor instead of a front panel full of switches and leds was a lot cheaper, though it did force you to have some sort of teletype or terminal to use the machine. The SS50 bus using Molex pin connectors was cheaper than gold fingered card edge connectors like the S100 bus used. The machine was simpler, easier to understand and a lot could be done with it. The 6800 was an under appreciated 8 bit CPU for its time.
As was the 6809... (probably the most powerful 8-bit CPU)... unfortunately it wasn't cheap enough fast enough and it was overshadowed with the release of the MC68000 in almost the same time period, so few machines actually used the 6809.
This was the very first microprocessor system I was introduced to in 1978 - in my second year at university, which had a set of them for students to learn 6800 assembly language on.
SWTPC advertised heavily in Popular Electronics magazine in the 1974-1976 time frame. I remember seeing their ads for this kit.
Mid to late '70's, those were the days 🙂
A friend of mine built one of these SWTP's.
.
I made a home-brew TMS9900 from scratch.
That was a good learning experience for both hardware and software.
Even back in the 70s there was an Intel vs Motorola vs RCA community.
The S100 Buss was predominantly Intel 8080, 8085 and Zilog Z80 based, whereas the SS50 and non-S100 systems were predominantly Motorola and non Intel based.
Of course each Chip Company had their own proprietary Development Systems, varying from bare-board SBCs to fully assembled Systems with Professional Cases, Serial Terminals/Monitors, Dual 8" Floppy drives, DB25 Serial Ports, DB25 Parallel Printer Ports (Centronics Interface), and In-Circuit-Emulators (ICE).
The Intel iDS was one such offering which was used to develop Software and Hardware for Intel 80xx 8-bit Processors and Microcontrollers using the Intel Development OS, Assemblers Compilers and launguages such as BASIC and PL/M. It also ran Digital Research's CPM-80 and many CPM-80 supported softwares such as WordStar and Microsoft Basic.
There was a huge offering of SBCs, Built Systems, and Ancillary Boards and Peripherals in the late 70s and early 80s.
Nice, years ago a work collegue had one of these (but in a wooden box). I wanted to get into the 6800, and this SWTPC machine had all I needed. So I grabbed a copy of it's memory map and I kind of cloned it.
Apart from the disk controller, I didn't copy their design, I used my own design, that perfectly copied it as far as software was concerned, so I could use all their software.
Mine was built entirely with wire-wrap, it had 3 serial ports, floppy, and 40KB of static ram using 2K ram IC's (6116).
I also built the floppy drive into the enclosure, but with provision for an extra external drive via a 37pin 'D' connector.
Pity I cannot post photo's here.
There are plenty of online groups, I'd love to see the photos of your machine.
@@hyretechHere is a quick youtube video clip of photo's of my SWTPC 6800 clone
It is 99% wire wrapped - th-cam.com/video/3JJU8ENm8bk/w-d-xo.html
One of these days I should pull it out and see if I can get it going.
The wire wrap still looks good after all those years, unlike some commercial products I've seen that look quite tarnished. repairing corroded wire wrap wiring has to be one of the worst things.
I tried posting a link to an article I wrote about it, but the post 'would not stick' - it's now in the notes of that TH-cam video.
My Grandpa did a lot of wire wrap circuitry in the 70s with 16 pin DIP ICs. It looked like a gigantic PITA to young me and I never warmed to wire wrap before it kind of faded from the experimenter's scene.
@@lironmtnranch4765 Wire wrap was also used commercially, back when I worked for Telstra about 30 years ago, we had at least two models of high speed modems we leased to customers that were entirely wire wrapped in their construction. They were packed tight with boards, all wire wrap.
Ah, the good old days!
I have the 6809 model - not just a CPU upgrade; the enclosure is a newer design, and I think there were several other differences.
It's in storage these past many years, after having been my primary computer in college.
If memory serves, I got it with 8K of SRAM, then wire-wrapped a 48K DRAM board.
Got the standard dual floppies, plus a kludged-on double-the-tracks drive.
I should dig it out and refresh my memory on what else is in that box. I have a vague recollection of running a wire from the power supply to somewhere-or-other to get a 60 Hz interrupt.
I've got a couple of the SWTPc 6809 chassis and a box full of cards. These were made around 1981, and I know that SS-50/SS-30 bus machines were in use into the late '80s, especially ones from GIMIX. The 6809 machines could run the same multitasking, multi-user OS-9 operating system that ran (as an option) on the Tandy CoCo line. With all those expansion (slots? not really slots) you could have quite a few terminals, and a Level II OS-9 system running at 2MHz, with up to 1M of RAM and a dynamic address translator could support a surprising number of users. One fascinating card I have among my collection is a board for the SS-30 bus that contains a National Semiconductor calculator chip, which serves as a math coprocessor for the CPU.
The (D)OS most commonly used on the 6800 was called FLEX, which was essentially the 6800's answer to CP/M. There was also a version of FLEX for the 6809, as well as UNIFLEX, which, I believe, was an attempt to make a multitasking UNIX-like version of FLEX. I don't think that one saw much use though, since OS-9 did the job it was meant to do better, and was endorsed by Motorola. The source code to UNIFLEX is available on the Internet.
There are modern SS-50/SS-30 reproduction cards, and Corsham in the UK sells high capacity static RAM boards and CF card 'hard drive' interfaces.
One thing to be careful of on these systems is that forest of pins. It's extremely easy to consume fuses on that backplane by bridging between pins with a screwdriver or some other metal tool. Ask me how I know.
A great resources for these machines is the magazine "'68 Micro Journal". Scans can be found on Internet Archive.
TH-cam seems to 'disappear' posts with those newfangled hyperlinks. Hey YT, welcome to 1994.
First of all, got to mention the sweet 6809 from their later years that LMNC has.
Yeah, you have a very early SWTPC. And having a resident monitor standard instead of a front panel was a big innovation that happened in those few years since Altair and IMSAI. (In between was the keypad/7-segment style like the KIM-1 and H-8.) I guess ROM chips for a monitor program finally became affordable or something. Note that 1977 was the dawn of the Atari 2600, which made mask ROM chips a big business.
That floppy controller is enormous. I have one that I found on a 30-pin card, where some fool tried to fix it by piggyback stacking chips.
As for the price, the original TRS-80 Model 1 4K was $599, also in 1977. This was a time when even a single year brought major advancements in bang-for-the-buck.
I was living in San Antonio since 1979, but never had any idea to visit them back in the day. I'm kind of sad that I didn't, but I didn't even have a driver's license until 1981 or so, and I was firmly in the Radio Shack camp the whole time. By the time I realized they were there, they were gone.
Apparently the final two boxes of SWTPC repair parts (chips and other small parts) ended up at the 10bitworks hackerspace a few years back (I was there the day they came in), but with how hackerspaces are about "junk" taking up space, I have no idea if they still have them.
I bought my SWTPC in late 1977. Parts started arriving in 1978. By September I had a running machine. It was purchased with 8k of memory. I got 4K Basic on a floppy ROM. I also made the CT64 Terminal. Around 1980, I got floppy disks for it with the DC3 driver board. As a HAM, I got on the internet around 1984. At the time the ARRL had a class A to its self. One of the local HAMs gave me my own subnet. I got up and running on AX.25. I found a way to make AX.25 unreliable and was able to run Telnet and FTP. On the 2 meter band through my 2 meter radio and a MFJ-1278 Terminal node controller I was up and running. The last thing I did with it was to design and build a 48K memory card. It still works. I also got the GT6144 graphics terminal and an Atari 2600 joystick through a parallel port. I wrote a crude PAC-MAN program. My first checkers program was written in the late 1970's. It used the inhex 2 character routine to enter moves.
Boy - this channel brings back great memories. I built my first kit computer sometimes in the 70's. It was a Z80 S100 kit board and a 1K static memory board. I built my own power supply and chassis and got one of the first TV Typewrite kits. It was wonderful - something like 15 lines of 32 characters - but it was a lot better then programming with front panel switches. Over time I upgraded it with 8" floppies and better monitors and I actually used it until the 90's when I gave it to a friends son so he could learn computers. Those were the days!!!
That is a total gem. I never heard of them back them (I probably saw an ad for them), but was hooked as soon as i saw the Altair on the Popular Mechanics cover. I held out for the Vic-20 and when it hit the magazine pages, with a full keyboard, color, and graphic character set, I was ready to throw money at them, and I did. Not easy as a 14 year old kid to come up with $450 for the computer and datasette (saving Christmas and Birthday money - I had no job - so it took me quite a while to save up).
People don't grasp today how unbelievably weighty the keyboard factored into your purchasing decision of which computer to buy. It seems laughable now when you can plug any keyboard into any PC, but back then when you were looking at Sinclair and Atari membrane keyboards versus say a C=64, yeah, you see, the keyboard was the killer feature.
You wanted something you could pound out tons of programs on, and then be able to save them and retrieve them reliably. Because you didn't have money left to buy any software - there was no software - you were going to have to write it all your own.
A lot of these are stored in temperature uncontroleld barns or sheds as junk. I use to say comptuers came to me to die and I got them all in the end. I've got a dinosaur elephant graveyard of them, all neglected. Back in the day I would of killed for any one of them. Now I can't stand to even look at or touch the wretched old things, the memories are too painful.
A Commodore 128 or Mac Plus back then would of been a wonderland to me and there wouldn't of been any coming back from inside those machines. My granparents gave me a C-64 out of the blue next xmas, and after a hiatus... my next computer was a Mac SE. From the Mac SE I went to a 386 and a Performa 476, and from there it exploded ito bringing home comptuers by the pickup truck load.
I used the SE to write programs to earn money to buy the 476, and then used the 476 to ask universities and businesses for all their junk computers. Sprinboard, springboard... like jumping stones in a creek.. to computer empire hog heaven :-) Halcyon days back in the roaring 90's...
for a perpeetually unemployed kid.. I was living my version of the Steve Jobs dream. 40 years before that blad 8bit guy ever came along. LinusTechTips had nothing on me. In fact, if I hadn't changed directions, I would of ended up that 8 bit guy, a sad endinge.. but I let go of these machines finally, and blazed a new trail always upward and forward.
It would be nice if I had a museum to put all this old hardware in... for dispaly.. I'd never have the time to refurbish any of it.
@MS-nj9le My mom almost purchased a Sinclair computer for me when I as 8 years old. However, upon seeing it, she decided to purchase a Polaroid camera instead. Years later at the age of 12 I discovered why I wouldn't have liked it. My grandparents let me pick up a used one at a yard sale and well, the membrane keyboard was flaky and I could only get one program to boot. I wasn't very interested in programming it. Then when I was 16 years old, my mom bought the family a Tandy 2500XL which came with Deskmate and programs I could understand. I was happy with it. If she would have bought a Commodore Vic 20 I probably would have been more interested at 8 years old. It only took me one time to never format the c drive again to learn that I shouldn't do that. Since then have fixed my own computers. I turn 48 in February in 2024,
My first computer build was a SWTPC 6800. Although I used audio cassette with the AC-30 to store data and programs, I later added an 8” floppy drive offered by SWTPC. The floppy drive used a parallel card. I bought a Xerox daisy wheel typewriter with an parallel interface to use as a terminal . Later I bought an ADM 3A CRT terminal and upgraded the RAM to 32K.
I still have the main unit and AC-30 stored in the attic along with the documentation.
I built a system based on the Motorola 6800 because I had worked at Motorola when the 6800 was being developed. The 6800 team recruited a colleague of mine to write a cross assembler for the 6800 that ran on the DEC PDP/11. The 6800 team leader was Chuck Peddle who left Motorola for MOS Technology where he developed the 6502 chip that was used in the Apple II and the Commodore PET.
I purchased the SWTCP kit and built this computer in 1976. I also bought the SWTCP CT-64 terminal kit and the AC-30 cassette interface kit for it. I bought a Radio Shack paper tape printer for program listings, because it was cheaper than the SWTCP printer. I never upgraded to a floppy disk drive, because by the time I could afford a disk drive, the computer was already obsolete. I studied all the computer kits on the market at that time and decided that the SWTCP computer was the best bang for my buck. Another reason for my decision was because Motorola made a complete family of support chips for the 6800 microprocessor, with excellent documentation on the chips, and I also believed the SWTCP fifty pin motherboard with Molex connectors was more reliable than the one hundred pin motherboard used in most other computers at that time. I also designed and built my own a 12K memory boards from scratch to go with the 4K memory board that came with the machine, giving me 16K of RAM total in only two motherboard slots, which was a lot of memory in those days. I used 4K static RAM chips on my homemade memory board, which I built using wire-wrap sockets. At first, I modified an old tube type portable TV set to accept a direct video input and used that as my monitor; it's amazing that I didn't get electrocuted with that setup. Later I built an RF modulator, so I could use any TV for a monitor and I built an acoustically coupled modem for the computer. At the time I built the modem, there were only a couple of BBS systems at computer clubs in the U.S. and none were in San Diego where I lived, so I had to make long distance calls to the East coast and Northern California to try out my modem. My homemade modem used an adjustable analog oscillator (not crystal controlled) to generate modem tones, so I had to tweak it on-line until I established data communication with the BBS stations. As a result, I got a nasty letter from the Common Carrier division of the FCC warning me to stop what I was doing. Apparently, I triggered some long distance telephone switching equipment while I was tweaking the modem tones and AT&T assumed I was using a Blue Box to try and make illegal long distance phone calls. So, I had to shelve that modem and wait until I could afford to buy a commercial modem to get back on-line. I purchased the assembler and memory diagnostics for the computer on cassette tape, and later I bought cassette based BASIC for the machine. I had to write my own programs in the beginning, which was good, because I was a hardware engineer with no programming experience and I learned how to write code on the SWTCP computer. I still have the computer and all the SWTPC accessory kits I built for it. And, I still have all the original SWTCP manuals and Motorola 6800 books, plus the hand written notebooks I created as I built the computer and taught myself how to program it. I even have the original software on cassette and a lot of the original advertising materials for the computer. The computer and all the accessories still work, at least they did the last time I tried to use them, which was about seven years ago. I'll never forget how excited I was back in 1976 when I turned this computer on for the first time and the MIKBUG asterick appered on the TV screen. What I learned from building my SWTCP 6800 computer actually helped me get jobs, including one at Findex Computer, which was another early microprocessor based computer company that folded in the nineteen eighties. But, working on Z-80 systems at Findex helped me get other jobs in the early home computer industry that helped to springboard my career. I'm now in my eighties, and I hope I'll be able to find a computer museum that will take my computer with all the accessories and documentation before I kick the bit bucket, because it may be one of the most complete, unmodified SWTCP computer systems that's still in existence.
I worked with this computer for a number of years. it had 2 floppy drives and a printer that we used to print labels of pay-slips envelopes.
I know 2 people that had their own systems. I will ask them if they still have documentation etc
All I remember of SWTP was when a work buddy brought one over to get it working, I was shocked at how long the 6800 BASIC interpreter took to boot compared to my 6502 KIM-1 machine.
Perfect video to watch while working on Arduino code for my first soldered breadboard computer!
I am so intrigued by this machine. This is so different, and yet the same, that it makes be smile. I am on the edge of my seat to see how it works out.
Thank you so much for producing this video - it brought back so many memories from when I'd just graduated in EE and courses in digital electronics and computers were rare and new, often with xerox'd handouts rather than textbooks. I read all the magazines but a new engineer's salary still couldn't touch even the kit versions. I discovered the Motorola MEK6800D2 evaluation kit and begged one off of a Motorola engineering rep over the phone (still had to pay for it).
Not my first electronic assembly but it didn't work when I finished. I found an old Army electronics technician who let me watch as he went over the circuit carefully - he discovered two traces shorted together where the etching was incomplete and scraped it with a sewing needle until the kit leaped into life! 128 bytes of RAM which I upgraded to 256 bytes after waiting for my next paycheck.
Display was a huge issue since terminals were way too expensive as were TV modulators. The 'D2 kit got around this with the included hex keypad and LED display - I learned to hand assemble 6800 code and remember typing in a program for 10 minutes while a friend watched. It worked but all it did was blink one LED! My friend almost hurt himself laughing and told everyone the story anytime the subject 'computer' came up.
Sadly the 'D2 was recycled at some point. I'd love to have one now but they are way too expensive on e-Bay. My career included only using computers (not designing them) but they made an interesting hobby. I look forward to your newest videos and again - thanks for the memories...
Honestly that's a really lovely bit of design, a modern build in a case looking like that would be really great. Understated yet very cool :D
I saved one of these from a similar eWaste fate a year or so ago. I had no idea what it was when I got it. I really like the 6800 design. For me it was like the precursor design to the Apple 1 or 2 because it had addressable expansion slots and a ROM monitor. It’s a proper old computer. Looking forward to you getting this one working.
I remember using one of these in the store "Digital Design" in Cincinnati, Ohio. Daniel M. Petersen was the owner of the store, and he tolerated teenagers hanging out.
The SWTPC box was available to rent for 50 cents an hour, cheaper than a video game.
The store also sold Alpha Micro, IMSAI, and Apple II machines.
The BASIC language didn't support the SQRT function, so another fellow - a UC student - suggested writing Newton's method in BASIC to solve the problem.
It worked.
The 6800 was the top of the line 8-bit CPU. It had more registers a more flexible design than the 6502. This made it more expensive. The software console was actually a rather late enhancement on the mini computers of the era. such as the PDP-11 series. These computers were used for business and lab work. The 6800 put much of the power of a " Real Computer" in the hands of the home builder. This was a rather full configuration. With the floppy drive box it would have been a very powerful home PC. It will be nice to see more done with this beauty. I was taught assembly language ob a P?DP-8 mini computer system not much more powerful than this one. I mention Minicomputers because that is what the "Small Computers" of the time were. Minis were also vastly more expensive. I grew up with machines like this, in Byte magazine and dozens of others. Thank you for showing a machine I dreamed of, out of high school. Good luck and God bless you.
Not sure how you make each post "routinely brilliant" but thank you!
Never had one of these as they were way before my time. But my father was an audio junkie back in the day and he bought and built a couple of the SWTPC power amps he got from a mail order kit. I still have them and they still work!
Back in the late 70's, my father (who I just e-mailed the link to this video) had one of these! I don't remember the major details about it (I was a kid at the time -- just recently in elementary school), but I do remember he used it with a teletype keyboard/printer. And I DO remember the separate disk drive for it (I think it was the same maker, but I only remember it having two drives rather than three).
I worked with a 6809 version, Gimix. It ran OS/9 a Linux clone. It was multi-user and multi-tasking. It ran rings around the first PC.
A technique I use to safely remove chips from eight layer array processor boards back in the 80's is to clip all the leads off as close to the chip package as possible. Then' one lead at a time, clamp a small set of hemostats to a lead, Let it hang down below the board while you heat the pad from above. When the solder melts the lead will just fall out. Then just clean up the hole with a solder sucker or wick.
Awesome to see a computer with no tiny Surface-mount technology (SMT)'s.
In the early 1980s I worked on a SWTP computer writing some code for a client! I never thought I'd hear about it again.
That is a total gem. I never heard of them back them.
Volume does not equal quality.
I really enjoyed this video! In Sydney there was a computer club called MEGS - Microcomputer Enthusiasts' Group Sydney, which was the first computer club in Australia. I joined it while I was at school in the 1970's. So much was above my head but it led to so many things for me - two jobs. Cheers
This brings back lots of memories from my late teens which developed my lifelong interest in all things computer.
The SWTPC's 6800 was loved by my vocational electronics class in high school. We built one. In 1976 our instructor had gotten one to build as a class project and it set several of us on our career paths. I am still working at a network engineer today nearly 50 years later!
This was one of the best in class at the time. Like often happens didn’t get the right press and was somewhat eclipsed by the 8080 based systems. Never the less was not an unknown by any means.
About a decade ago, I felt fortunate for finding an original empty computer case for an Altair 6800 from New Mexico. This machine release, I believe, 6 months after the original Altair 8800 hit the market back in the first days of home computers.
Fascinating stuff. I am looking forward to the next episode.
I actually have one of these amazing machines. I got it just last August with 24K of ram and the cassette interface. One note on the ROM and the terminal interface. You have the later ROM called SWTBUG, switch can run the terminal at 1200 baud. I used it on my VT320 terminal and learned a bit of 6800 assembly on it and did things like play games using the 8K BASIC. I hope to find a floppy controller that can hook up to my dual 8 inch shugart floppy drive enclosure that I use with my IMSAI. Once I find that I can run Flex, which is a really interesting OS, basically the CP/M of the 6800 world. Of course the next step for me is to finish the Teletype project, which is torn into 1000 pieces atm.
Good luck with all of that, and have fun!
Adrian, in the old Byte magazines (which everybody read way back when), the SWTPC was advertised all the time. They were still just for experimenters. It wasn't until the Apple II and the TRS-80 that it moved from experimenters to guys who could just tinker if they had a little bit of skills.
Many years ago (late'70s) I went to a local computer store and saw a table with used systems. One was a SWTPC 6800, and the other was an OSI (Ohio Scientific Instruments) C8P. Both were just the "boxes", and were priced the same (and I don't recall the price, but reckon it was around $300) but I bought the OSI because it used a 6502 CPU, and I was familiar with that chip, as I had built a couple of homebrew systems with it. I didn't realize what I had bought, as the OSI had the video interface board and the cassette interface, along with BASIC in ROM. I hooked up a keyboard, and modified a Sharp TV to be a monitor, and was running! Later in my career, I used a variety of 6800 variants, along with 6809 and 6811, but still recall fondly the old OSI. I wish I could remember what I did with it, though. If you are able to find one of these, I think you'll be impressed with its capabilities.
The golden years of home computing, back when you scraped together money and built your machine from articles in popular electronics and other magazines! Premade machines were for the rich, homebrewing was what many were stuck with, and this included writing your own software! Floppy drive controller, most had little use for such a dream product as they were glad to have a cassette tape drive and an old teletype grinding away. One school friend and his father built a Sol 20, his dad converting their little sony B/W portable TV into a monitor and a kit his dad picked up some kit to modify their selectric typewriter into a printer. I was amazed, and he even as a 7th grader, was writing software and doing stuff with it.
back when I was running windows 95 and having problems with it having to be restarted pretty often, one friend asked if I'd rather be working in IBM DOS instead and I thought back at the people I knew who literally had to spend days trying to get a piece of software working just to do one thing and it really showed how much had changed in just 15 years..
The 6800/6809 were "relatively cheap", but keep in mind the 6502 came into being and sold millions because it was less expensive than those cpus. It probably related to complexity and "yield". Excellent video though.
Yeah, the 6502 was designed by ex-Motorola engineers as a cut-down, low price version of the 6800. Their original chip was pin-compatible with the 6800, but Motorola sued, or threatened to, and that one was pulled and replaced with the 6502. If I understand correctly, the Apple 1 has sockets for either a 6502 or a 6800.
@@joelavcoco Yes, I think the original was the 6500, the redesigned one was the 6502. There were reduced pin count versions like (I think) the 6504 and others, one was used in the Atari 2600 as I recall.
I used to have the IC books from Synertek and many others from that era, but had to throw a bunch away after a basement water "event". A big thick Motorola one had the entire micropressor series, including a diagram using a 6809 and 6847(?) that was almost exactly the Radio Shack Color Computer design.
@@bobblum5973 Yes, the 2600 used the 6502, also the entire Atari 8-bit family, including the Lynx, the Apple II, Nintendo Entertainment System, Commodore 64, and BBC Micro
I remember this and the SOL-20 a business class machine of the time with 8" disks with a beautiful wooden case as well as the polywell 88 the little machine that looked like a flight data recorder and was ITX sized long before it became fashionable; and the aim-65 and Kim-1. God am I old!
Oh, wow! I researched the Imsai, Altair, SWTP and the Polymorphic 88 when I purchased my first computer back in the 70s. I still have the ad folders for each. I wound up getting the Poly88, and I still have it, although I haven't powered it up in years.
Great video.
I had one and hooked it up to a Silent700 terminal. I had no permanent storage other than cassette audio tape. At that time I made slightly more than $100/wk. The SS-50 bus generated so much RF noise, it disrupted all radio and TV in the house. Serial communication was actually done with a parallel interface chip by shifting, timing, and strobing the individual bits out. Later they introduced a serial card with a Motorola UART.
This takes me back! I left school in 1979 and two weeks later I started my first job in Hull as an apprentice computer technician. I cut my teeth on the SWTP 6800 and 6809 system -- I used to assemble them (usually into custom cabinets) and test them, before delivering them to customers. Always used to give a little cheer when a new system booted up and the '$' symbol appeared on the monitor!
Despite being named a 'home computer', they were more than that and were capable of doing serious work in a commercial environment. The company I worked for employed two software guys who wrote many bespoke software packages to run on the SWTP. They developed apps that covered everything from accounting to a SCADA system for a factory! That SCADA application is where I also learnt the art (and love) of analogue electronics, developing the interfaces for various sensors.
I also remember a 5MB Winchester hard drive that we interfaced to a SWTP system -- that beast required two people to lift it! Back then, to 19year-old me, 5MB seemed an inconceivable amount of storage space! Towards the end of my time in that first job, the new-fangled IBM PC came out, with twin floppy drives and 480K of memory! Happy days!
I can't help wondering what you did next. 8)
Fun fact: This exact architecture (Board style, chips and interface pins) were used in the first SS Arcade Pinball machines:
6800 MPU, 6810 128 x 8 SRAM, 8-bit ROMs to store program code, and an expansion board with 3 x 6820 or 6821 PIAs (peripheral interface adapters) to ‘read’ switch closures and output pulses to the lights and solenoids on the playfield. It was complicated stuff in the late 70s to early 80s.
I like the appearance actually. Very sleek, retro minimalist modern. Their logo is super cool!
The December 1975 issue of Byte has an extensive article on the SWTPC 6800. Interface Age was another great magazine during that era. SWTPC was all over back then - it was on the cover of the September 1976 issue of Interface Age.
I still have all those old issues!!!
In 1976, I designed and built a single board computer at work. I was the technician for the 8080A at National Semiconductor and was asked by my boss to create a demonstration board. I used an 8"x12" pin array board (full of tinned through holes on 0.1" centers) and wire wrapped up the 8080A, 2KB of RAM, 8KB of UV erasable EPROM, and a 20mA current loop (teletype) I/O. It took me one month from assignment to working computer. I left the company not longer after that and left it running, printing out "Now is the time for all good computers to come to the aid of their users." once every minute. By the time a friend came on the next Monday some 3600 lines of text had been chunked out on the roll of brown teletype paper. I do not miss the days of debugging mistakes on wire wrapped boards.
I remember that a DOS named FLEX was made for the SWTPC 6800, the late upgrade to 6809 could run with OS9 and I think they made a FLEX09 too.
SWTPC also mad a 68K version and for that system a FLEX68K was produced and much later a OS9-68K.
FLEX was very Unix like
OS9 was way ahead of both MS-DOS and CPM - at least up until '84. OS9 was fast becoming an embeded system OS and had a GUI before MS released Win 3
I think it is stunning in its simplicity.
Fascinating insight into 70's tech. Thank you Adrian, look forward to the trying-to-get-it-run video.
What a cool time period. I remember being interested in computers at this time and wanting to write software but being a kid I couldn't remotely come close to affording one.
I built one of these computers back in 1976, and it’s still sitting on a shelf in my basement. It was a great hobby and learning computer for do it yourselfers. I built my own keyboard with Cherry keys, and my own tv typewriter terminal. Eventually in 1980 When I was in fourth year university, I convinced my control systems prof to let me work on project for him for a credit, to develop a PID control program using my SWTPS computer, all done in assembly language. 1981 was start of my engineering career in computers and electronics, now 40 years later I am retiring, and still mess around computers and electronics as a hobby.
Interesting.. You still have the same basement you had in 1976?
@@TenableVegan same basement since 1990. Moved a few times between 1976 and 1990.
I remember seeing ads for it, the company logo, in magazines like popular electronics. I take it you have a TI TTL databook handy. Thanks for the video.
This computer is fascinating, I love the deep look at the hardware. This 6800 really seems like a playground for a nerd like me.
In 1985 at Durham University I recall building a MC68000 CPU control board. Everything was precisely wire wrapped and if you got it to work, it was then programmed with Assembly. It wasn't RISC but CISC (Complex Instruction Set) with 32 Bit instruction set and 16 Bit Cpu Bus
I remember going on holiday as a kid in about 1977 and really didn't get the idea behind what the machine was but wanted one.
No one heard of that? I knew about it. While I did not purchase that item from them, I use to purchase other products from SWTP. My CP/M system was cobbled together using the case from an Intel Intelec8 software development computer, a backplane salvaged from ???, CPU and memory boards from the Dayton Hamfest, and an IO card I designed using a S100 wire-wrap prototyping card. Disk I/O was a pair of 8" drives that used a voice coil to drive both heads at the same time! It was a beast. Track access time was much less than what a hard disk drive could do with a stepper motor. The only thing I never did was reverse engineer the BIOS so I could patch it to compensate for the fact that both heads changed at the same time. Switching drives always produced an annoying seek error. Fond memories.
Like the old Virginia Slims commercial from back in the day said, we’ve come a long way, baby!
The power in that computer is probably a fraction of what’s inside that smartphone you were using
This looks like a very interesting project you’re working on.
In my early days, I had a friend that had an SWTP 6800 and he let me play with it. Was able to get it to print out things using the MIKBUG firmware. I myself later bought an IMSAI 8080 as it was more advanced than the 6502. Today it is still working!!!!
I never attempted one of those, but several of my buddies were veterans of the Battle of the 680 Wires. For the time, it was one SWeeT PC!
You can make that missing trim piece easily out of a bit of aluminum angle stock. Some time with a wire brush will replicate the original finish.
I've never had this actual computer, but I remember ads for it in Popular Electronics. I remember one ad for a version of the BASIC computer language you could get for it...on punched paper tape!
The motherboard's card address decoding logic made sense for the 6800 CPU, since the machine language architecture of that CPU had no I/O instructions at all! Any I/O had to be implemented as memory mapped, using full address decoding, and regular memory read/write commands to input and output data. The card addressing scheme allowed the address decoding logic on individual boards to be simpler, usually just the lowest 12 bits.
Adrian, it looks like you could recreate those front and rear trim pieces from some small aluminum angle or U-channel. Cut a v-shaped notch and carefully bend the 90° corners, or cut them on a hobby sized miter box.
If Adrian do not have tools for that, I'm sure that a possible collaboration with The Geek Pub would end with best results.
Wow! Absolutely terrific video showing the innards of a great vintage computer! I just loved it right down to your discussion of each card and ICs. Fantastic!
Its somewhat interesting that back then the Altair 8800, the swtp6800 and the 1st Atari computer model (the Atari 800) all had the number 800 but different processors... The 6502 was everywhere. The Atari 2600 (or vcs) game machine (yes this was a simplified version), Apple 8 bit, Commodore 8 bit, Atari 8 bit and the Nintendo. What an amazing CPU! Simple, yet elegant. It has survived a long time
Your videos are so interesting, engaging and well made! Cheers! Keep up the great work Adrian! Thanks!
Hoy! I've heard of that one! And the next one was the IMSAI 8080. I built a Heathkit et-6800 trainer, too! ;)
Wow. That thumbnail just dragged me back almost half a century. The Southwest was either the first or second computer I ever used… that or a NASCOM-2. Admittedly I was only 4 at the time!
I remember the SWTCP 6800. Well. We built a company around supplying cards for the s-50 buss,
I recently got an Altair 680 which I guess is Altair's version of this. 680 is also based on 6800 and serial, but it was much smaller. I would love to see some youtuber make a quality documentary about those early compuyters.
Adrian, thanks for reminding me of my misspent youth. The SWTPC 6800 is a great computer but it suffered one major problem: Molex disease. To keep costs down they used tin plated connectors that would tarnish, leading to bad connections. Third parties offered gold plated replacement connectors.
The Altair S100 and SWTPC SS50 weren't the only 8 bit busses of the mid 70s. Motorola had it's Sherman tank of a 6800 development system called the EXORciser. It sported a bus based on standard 86 pin .156" pitch edge connectors. Up through the 6809 era there were third party boards that used the bus.
The EXORciser was an expensive system, especially with 8" floppies, teletype console and/or $1000 dumb terminal. A brilliant move on Motorola's part was to sell the MIKBUG/MINIBUG program housed in a 6830 ROM. This allowed SWTPC to develop its computer sans switches and lights and yet have serial I/O and debug tools. All without having to write firmware themselves. I seem to remember that you could buy the MIKBUG chip alone.
While the EXORciser was aimed at industry, Motorola did not forget the amateur. In 1976 hey used EXORciser's bus on the MEK6800D2 kit. ( I could never watch Star Wars without being reminded of my beloved D2) At $300 it was a true single board computer, with 640 bytes RAM, serial communication chip, and It's own monitor/debug ROM: JBUG. On the top edge there were 2 50 pin ribbon cable compatible edge connectors, each wired to a 6820 16 bit parallel interface chip. The remaining 10 sq. in. of the board was devoted to a user prototyping area. The kit, came with a ribbon cable that lead to a PCB with 6 seven segment displays, a hex keypad, 8 function keys and a cassette interface for mass storage. I spent countless hours banging and debugging hand assembled code (branch calculations anyone?) into that keyboard.
A bit later Motorola developed a video interface chip, the 6847 that made it easy, with an RF module, to display data, in color, on a standard TV. New chip, new development kit, the MIcro Chroma 68. It came with, "The new "bug" from Motorola, TV bug 1.2" The board also had the familiar 86 pin edge connector that I assume, but can't confirm was configured as an EXORciser bus. I never owned a Micro Chroma 68 but I used the 6847 and cloned TV bug ROMs in my own hand wired systems.
Adrian thank you for saving a fascinating piece of computing history. Your channel is a joy.
I have a SWTP amplifier which I repaired. SWTP stands for SouthWest Technical Products and they sold affordable kits.
Thanks for the wonderful video. It's awesome seeing you work on these old machines. I've been following you since the first pc off of craigslist videos. You have come along way.
Awesome piece of computer history you have there. Thanks for sharing.
If I remember correctly when I was a kid in the 70s SWTPC 6800 was in the adds in Popular Electronics magazine.
as far as the 6800, I used the HP 9825 (6800) to drive instruments. HP was an instrument company at that time the 9825 used a private instrument buss HPIB (now IEEE 488) to control instruments. I did some great work with that family that defined me.
What an awesome walk through history this was... thanks!
During the time SWTP was in business I bought several of their kits, still have two in use. I wasn't aware they offered a computer. Interesting, look forward to seeing it in operation.
Great video! I always enjoy seeing the older "founding father" type machines still working.
Thanks for video on SWTPC computer. I have heard about the computer, I have never seen actual example, nor a survey of its hardware. Thanks for the video and keep up the good work!