Searching for bad RAM on a 45 year old SWTPC 4K RAM board
ฝัง
- เผยแพร่เมื่อ 30 ก.ย. 2024
- This is part 3 in the SWTPC 6800 computer series. In this video, I teach myself how to test the 4K RAM board and then figure out what is bad on it. This is all a learning experience for me!
Part 1: • The 8-bit home compute...
Part 2: • Let's try to get the S...
Part 3: This part!
Part 4: • We can fix it! A home-...
--- Video Links
Mike Douglas's TH-cam Channel with lots of videos on the SWTPC 6800:
/ @deramp5113
South West Technical Products Company:
en.wikipedia.o...
The SS-50 Bus used in this machine:
en.wikipedia.o...
Adrian's Digital Basement Merch store:
my-store-c82bd...
Adrian's Digital Basement ][ (Second Channel)
/ @adriansdigitalbasement2
Support the channel on Patreon:
/ adriansdigitalbasement
-- Tools
Deoxit D5:
amzn.to/2VvOKy1
store.caig.com/...
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.co...
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...
TS100 Soldering Iron:
amzn.to/2K36dJ5
www.ebay.com/i...
EEVBlog 121GW Multimeter:
www.eevblog.co...
DSLogic Basic Logic Analyzer:
amzn.to/2RDSDQw
www.ebay.com/i...
Magnetic Screw Holder:
amzn.to/3b8LOhG
www.harborfrei...
Universal ZIP sockets: (clones, used on my ZIF-64 test machine)
www.ebay.com/i...
RetroTink 2X Upconverter: (to hook up something like a C64 to HDMI)
www.retrotink.com/
Plato (Clone) Side Cutters: (order five)
www.ebay.com/i...
Heat Sinks:
www.aliexpress...
Little squeezy bottles: (available elsewhere too)
amzn.to/3b8LOOI
--- Links
My GitHub repository:
github.com/mis...
Commodore Computer Club / Vancouver, WA - Portland, OR - PDX Commodore Users Group
www.commodorec...
--- Instructional videos
My video on damage-free chip removal:
• How to remove chips wi...
--- Music
Intro music and other tracks by:
Nathan Divino
@itsnathandivino
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One note from me:
* I didn't notice on the schematics it did show which other 2 chips make up that bit. It initially only shows 2K of RAM chips, but the bottom it shows which other two chips are on the same bit. I should have swapped 4 chips looking for the bad one. Luckily I got there in the end.
OK this one time, but don't let it happen again.
How did you not hear me shouting that at my computer?
Adrian: 128 bytes not enough RAM to do anything serious
Atari 2600: I disagree.
8051 MCUs also disagree. Many industrial control units use this one to this day.
@@adamw.8579 I did some reverse engineering on a couple of 8051 based control systems lately, and to be honest, all of them used external RAM as well (not saying that every 8051 based design out there does, just all of the ones I happened to come across). One of them apparently had the C compiler used to create the program even setup in a way that everything that was not stack, register or memory mapped IO reside in the external RAM. Even stuff like loop variables, which I thought was quite inefficient. And it even had 128k of external RAM that it did access via bank switching, using an I/O line as address line 16.
As I understand it systems like the Atari 2600 and 8501 could do so much because the code could be read from ROM (or flash in the case of more modern microcontrollers). If both code and data needed to share 128 bytes, I seriously doubt you could do much. 128 instructions is really not a lot, and that's the absolute best-case scenario: all opcodes, no operands and no data or variables.
@@andrewsprojectsinnovations6352 8051 is a Harvard architecture - separate code and data spaces. Usually 2-8kB code ROM/FLASH max.64kB, and internal 128 bytes RAM, additional RAM may be installed with cost port 0 and 2 used as address/data multiplexed bus for external ram up to 64kB. Some simple units - for example intelligent peripheral use all ports and only internal 128bytes of ram or 256 in version 8052.
PICs also disagree.
Nice work. As a coincidence, I'm working on an FPGA recreation of this system at this very moment.
Nice! I wrote an emulator for it, also for Motorola Exorciser (search for "exorsim"). Your FPGA should connect to a real floppy drive :-) Recently I want to make a cassette tape interface like the SWTPC AC-30, but higher baud, more modern modulation.
@JENNITA B.O Be-gone bot!!
@@jhallenworld The FPGA card has an SD card so I can do stuff on that if I take it that far.
@@NathanChisholm041 Report, don't respond.
Hi Adrian. Your part 2 is still showing that part 3 is coming soon. Btw I'm loving this series and trying to guess / diagnose the fault before it's revealed. Great fun.
Hi Adrian, I’m from Germany and watch you channel basically for the Commodore Stuff. I really like it. But now to SWTPC, in the 80/90 th. I worked a Lott with this heavy Systems. The where used for logistics in Pharmacy/Drug Stores here in Germany. And the company I worked for also wrote some Software for accounting and billing. Usually first we used double 8` floppy disk drives and later also 5 to 10 MByte Harddrives. There where tripple density controller for the Floppy Drives wit a capacity of 3,4 MByte, which was amazing for this time. I really like this SWTPC Videos, great job 👍
Great description and tour of the various memory test programs. I never had the patience for them where the RAM was socketed.. the video card on my digital group system uses 2102s so I'd just swap chips from the 6800 to that and if I saw corrupted video I knew I had bad ones. Once I had those vetted I worked from there. I feel so lazy now.
LOVE your SwTPC (SwatPuck) series. I have one of these - home-built. It is in storage.
For replacing bad 21L02 memory chips - go to Electronic Goldmine and search for 21L02. They have a 'new old stock' of TI chips for about $7.00 each.
I also have original documentation - in a notebook. Schematics on most of the boards.
I built my SwTPC when I was about 21 or 22 yrs old - didn't know what I was doing. Bought the bare boards and the parts. I think I socketed everything. Miraculously, the computer powered up with very few issues. I had to add a 0.33uF capacitor on the +5V regulator on the main board - it was oscillating.
I had 2kRAM - and had to expand it to 4kRAM so I could run Tom Pitman's Tiny BASIC - that came on punch tape. I had an ASR33 teletype. (It took about 5 minutes to load)
I originally started out with the Video board that SwTPC offered. I also soldered that one together and got it to work - providing video to a 9" SONY TV that I soldered a wire into and fed the video into. (You could switch the TV to a blank channel on the dial.)
The keyboard I used was a kit that Radio Shack sold for a brief time. I assembled it and wired a cable from it to the input of the video board... or was it to a plug-in card on the SwTPC? IT's been a while ago... I don't remember.
The computer boards - I fabricated my own housing for them from plywood - it was about 24" x 24" square and 10 - 12-inches tall.
I designed my own power supply - probably not acceptable by todays standards - and barely acceptable back then, but it worked.
I never got any floppy or hard drive storage, and only used paper tape for my storage.
When I finally upgraded my computer, I went with a VIC-20 which had as much memory (RAM) as my SwTPC but also had color and other features that I could not get on my SwTPC - like cassette program storage.
I'm sure that there are others here who can help, but if you need any details on your 6800 SwTPC, feel free to contact me. I'm on LinkedIn.
I used to run quite powerful IBM RS/6000 machines connected to the serial when I worked at IBM. Lots of those machines did not even have a graphics board in their config.
Not only does that centralized clock save on chips, it also ensures the various clocks will be in sync between all carts, something you can't really do when every cart has its own clock.
True - and with the really moderate clock speeds of the era, you don't need to worry about adverse effects that the long connections between clock generator and clock user may cause, or even getting out of phase because the connections differ in length. With today's speeds, such an approach would be much harder to implement.
@@Colaholiker Another nice thing is, that with the 6800 bus you can easily share the bus between two masters. The CPU is only accessing when this clock is high, so the bus is free when its low.
Was for example extensively used for graphics which accessed the shared memory in between the CPU cycles.
Thank You for making this videos for us, I truly enjoy watching You tinker and repair all this good stuff. As always, great video!
Several suggestions here as to better ways to approach the problem but what you did replicated the efforts of hobbyists when this computer was new using the tools they had available. There was no laptop just a dumb terminal and each test was loaded via audio cassette (a real toss of the dice each time you hit play!). This video would have represented hours of effort but that was the hobby at the time. Adrian, even your unfamiliarity with the system is reminiscent of that of the original owner!
Very interesting way of troubleshooting, using the provided diagnostic tests as the "keyhole" into the system, and sure a great find to point ot the one bad chip.
When it comes to video length, I wouldn't even mind a day-long video. I know, this is not at all feasible, but watching you troubleshoot this retro stuff is just something I will never get tired of. ;-)
Way back then I built a Z80 system from magazine plans. The 4K RAM card used 2102s.(1Kx1) I designed a new version using 2114 chips (1Kx4). I keep thinking about digging it out and doing an "anachronistic restoration" on it by pulling both boards and adding one of those 32Kx8 CMOS RAMS to the Eprom card.
@36:12 I'm sure you are aware of it, but I think it is important to state it explicitly: You can get false *positive* readings (i.e. "is OK" when the RAM still has issues), but you can *not* get false negative readings. If the memory test claims that "memory is broken", *something* in your computer, likely the memory, acutally is broken.
PC component vendors like to claim otherwise if they don't trust your memory test and try to reject returns due to the test being "incompatible" or reporting a false reading. For example, the German computer magazine c't reported about low-quality SDRAM modules around 1999 and people started testing their RAM with extensive tests. There was a notable backlash against the c't report because some vendors were unhappy with the increased amount of "your PC has bad RAM" claim. In one of the follow-up issues, they published one or two letters to the editors by upset vendors.
I think that RAM board can be replaced with a 6264, 74HCT138 and 7805. Could provide 8K bytes of RAM of course.
Another great video! Maybe consider doing an extended version (part 2) of some of your videos for Patreon Patrons for those of us who like the long-format? An Adrian "After-Party" if you will?
20:08 "Computers are simpler now...." - Well, they are when they work, but the average user has no chance if they stop. A tinkerer could figure out a hardware fault by swapping boards in a desktop pc, but if Windows decides not to play, it's a whole different ball game. Tracing bad RAM chips on a board is child's play in comparison.
The 21L02 chip is used as video memory on the TRS-80 Model I. The Model I only provided 7 bits of video memory. We had t piggyback the 8th chip and do some minor mods to the board to enable the 8th bit and with that, lowercase.
These early computers required machine level understanding like Adrian has. An obvious opportunity for development to more accessible higher level languages.
I know someone who, when they were 12 years old, got a mouse. His dad called them to see if there was a device driver to go with it and the response was that if his 12-year-old didn't know how to write a device driver for it then he didn't deserve to have a mouse. Ah, happy times. I do miss having schematics for electronic devices though.
The control circuitry for my coffee maker failed the other day which was no big deal because I wanted to control it via networking, 12V and an inverter anyway but the company wouldn't even tell me what the wires were because "it would invalidate my [non-existent] warranty" and "for safety reasons".
That's why I tend to use very old electronics stuff. I can get schematics, and I can repair it. No amount of 'new' and piles of sophisticated features is of value if something doesn't actually work and can't be fixed.
Reminds me of a certain type of Linux head who insists you compile everything and somehow know not to accept the default compiler flags for 1 in every 12 package..!
Someone watches Louis Rossmann.
@@ImpetuouslyInsane Yes but I wouldn't touch Apple's overpriced, underspeced and locked down products with a 10' pole. No prizes for guessing my OS of choice!
Several hours into this series, I've come to the conclusion that this machine is a step too far for me. Good on your enthusiasm, though, and I hope you enjoy finishing it! 👍
That mem board was hovering dangerously over that huge capacitor
Thanks for the SWTPc videos. I built one back in college which I still have. I has some spare 21L02 chips from way-back-when. Let me know if you need one to fix that board as I think that they are a little hard to find.
I really enjoyed watching you troubleshoot this machine. I would love to see it do some practical work.
Modern computers are easier when they work, but the one I just built has gremlins. Newer hardware pushes itself so hard it's always on the edge of failure at stock clocks, but because it's consumer grade, reliability isn't a concern. Nothing adequately diagnoses itself. When something fails and you don't know which part, just buy new stuff until it works. The industry likes it that way.
Now I wonder, while doing the troubleshooting in this way, using the tools that were available back in the day is an experience of its own, since all the chips were socketed, couldn't you just run all of them through the Retro Chip Tester?
I'd love to see a breakdown of what those memory test programs are actually doing. It seems amazing that so few instructions are actually testing the memory in the machine! Loving this series, as it is from the era just before I started using computers (my first was a Commodore 64), so it's fascinating to see. This particular machine seems to be remarkably elegant, although I'm not familiar enough with its contemporaries to know how special the SWTPC is.
I'd guess it's not much more than an idiot simple 'write, read, compare, print, increment' routine using FF and 00.
I've always heard SWTBUG pronounced as "SWAT BUG" from SWTPC 6800 power users.
I'm surprised you don't have any 2102s in your collection. As I recall ,those were the most common RAM chip in computers of this era, before the 41xx series DRAM chips came to dominate with their higher capacities.
When I see that computer I still think of my friend Judy, who had one. Thanks for working on it.
Not as fancy as OS9, but my friend used to run FLEX this: en.wikipedia.org/wiki/FLEX_(operating_system)
Images/Docs: www.simonwynn.com/flex
Looking at the hardware on the computer, and at risk of seeming like shill, I am reminded that Evaporust really would take that rust off pretty well. I used it on a tray of assorted hardware. It may remove black oxide, but for hardware with other kinds of plating, such as zinc-chomate, it seemed to leave it intact, while doing a pretty good job. Afterwards the hardware could be sprayed with something to protect the rust--or perhaps a thin coat of lacquer would also protect it, as long as it's sprayed outside with proper breathing protection. I prefer lacquer because it dries harder and in a shorter time. I run the remainder back through a funnel and a coffee filter--before putting it back into the container. Although Evaporust is safe, like vinegar, it's PH means that it's not good to get into cuts. I think that Rustoleum also has their own chelating rust-remover too, that might have greater availability.
Also, I had an experimental idea: cleaning boards in an ultrasonic cleaner, but with a twist, of using some Kool Mist mixture to prevent corrosion whilst cleaning. It should prevent rust from forming. Kool Mist is a fairly safe chemical that can be added to distilled/dionized water that allows steel and iron to be soaked in it to prevent rusting. It's mixed about an ounce to a quart. After cleaning, the board could be blown out with either compressed air--or small handheld leaf-blower.
Start by clicking each chip in its socket. This stuff happened back in the day too.
Loved this video Adrian: the diagnostic, the mental process followed, the different hypothesis tested, all of that topped with your own vast personal experience and as always your very engaging storytelling and explanation of everything you are doing. YOU ROCK Adrian, thank you, thank you, thank you!
*Adrian
@@Plarndude thank you and corrected! I don’t know how I missed the misspelling of Adrian’s name.
17:14 the subscript 16 actually is the base of the number, so that is 20 in base 16 (hexadecimal)
i think the long format videos are good for things like this since it's not a device featured on the channel alot
I have some old ram testers...but not that old..unless you desolder the chips and test 1 at a time.
If you think about it, in some ways computing has returned to this early structure with the popularity of credit card sized computers such as the Raspberry Pi and Arduino. The biggest difference is the also include a mass storage system in their tiny form factor. It requires an external terminal to access just like these old computers. They are mean to be interfaced to the real world through GPIO.
12:51: If I understand correctly, this means it's big-endian, right? Am I wrong?
Correct. Motorola used big endian in 68xx and 68xxx series.
@@robertdixon8238 Thank you. :)
(Also, I'm facepalming a little at my own stupidity to have not caught on to the obvious M6800-M680000 connection, because I kind of knew that about the M68k.)
This is badly making me want to start working on my CompuPro 8/16 S-100 system again. I think the only ROMs in my system are for floppy booting, I wonder if there are some diagnostic ROMs out there I could find?
Gotta laugh that your chip tester probably has many times more computing power than the computer!
Really enjoying this series. My computing history starts with the VIC-20 and Apple II+ so I have virtually no exposure to something like this. I like to be able to appreciate what the people before us had to go through to enjoy the hobby or process actual work at a company.
If you ever run out of things to fix (haha, I know) I'd be fascinated to see what you could do with late 70s early 80s arcade game PCBs. There's lots of variety there as, especially early on, the boards were basically single purpose computers made for just playing that one game. The concept of "cartridges" or something similar didn't show up until maybe Sente in the early/mid 80s as far as I know.
TeraTerm allows you to directly send files (just drag&drop the whole file into the Terminal window), so you don't need to copy/paste from the file manually.
i use that myself to load .bin files via serial onto my 65C02 SBC and it works great
I have an original old SWTP dot matrix printer! You are welcome to it if I can get your shipping address. The printer is in working condition but you would need the driver software for it. Quite a collectible piece of computer history! I think it was the first commercially available dot matrix but am not sure.
This is a pretty interesting repair. I've got a breadboard Z80 project that's similar in a lot of ways. I got a kick out of part 2 on the serial stuff bcz I knew exactly where that was headed as a oldster telecom engineer.
This is so much fun! I'm enjoying your journey with this computer. I can't wait to see it run basic!
Back in the late 70's, I used a Motorola 6800 D2 evaluation kit to programme a complete radio paging system in machine code. The data storage was with a cassette tape, for which I used my own cassette recorder. I had to build an EPROM programmer from scratch to programme 2708 EPROMs with the paging code. They were 1k byte with three power rails, and needed multiple passes in order to programme each cell. The programmers were really expensive to buy back then. I still remember the weird ozone smell from the home built UV EPROM eraser.
The radio paging controller we made had a 7 segment LED display and a keypad. It connected to the paging transmitter and could control up to 1000 pagers on the system. Its code fitted into a single 2708 EPROM with space left over.
The computer you are working with I would have given my eye teeth to have then. Life would have been so much easier. Calculating branch offsets manually was quite a challenge, and testing the code was extremely time consuming.
I really enjoy your channel, Adrian. So many wonderful memories.
I owned a Color Computer which was great. It had a bunch of great business software and also a cartridge called EdTasm which is a 6800 assembly language editor/assembler. This is what I learned assembly language on. In fact, a company that I was involved in used the CoCo motherboard to make engine test systems for Cummins diesel engines at the 20 acre plant near Jamestown, NY. Worked great and really reliable.
This video took me back to my first real job. The company had a Cromemco 8", dual floppy system that was only a bit more capable than this SWTPC. It was primitive, but at the time, it was state of the art, and I loved using it.
Visited the Computer History Museum in Silicon Valley yesterday and was low-key excited to see that they have a SWTPC 6800 on display in their section on early personal computers.
I'm working on a heavily corroded board from a 60's camera. Heated 50% dilute Pine-Sol can do wonders. I use an ultrasonic cleaner with heater, but just hot soaking will shine up connections & boards well. It may remove weak solder mask though. But at that era, some boards don't even have it!
"Smoke Signal Broadcasting" is a rather ironic name for an electronics company!
Nice video. But at the end, I asked myself why you did not just test all the SRAM chips in the retro chip tester *at the beginning*? That would have saved you lots of time. :D
But it shows people that don't have a RAM tester how to debug this kind of systems.
It also made a nice video.
@@jorgwunderlich-pfeiffer1985 Exactly. He showed how a true engineer diagnoses an issue.
@@PJBonoVox Right - and he doesn't do these repairs for a living (at least the last thing I heard is that he has a regular day job), so he doesn't need to be as efficient as possible. Both this kind of repairs and TH-cam are his hobbies, which he shares with us.
@Timo Weirich Since his method obviously got him to identify the bad chip, it was not a "wrong" way ;-). I found this way much more interesting than just stuffing one chip after the other into the chip tester, and it demonstrated how limited the interaction with the bare core of that computer used to be.
Check electrolytic capacitors first.
@@johnbullpit9481 Why? If the power supply rails have low ripple, they are OK. There is no switching power supply that requires low ESR electrolytics and capacitors were better quality back then.
That was interesting. Like to see you find a replacement for the chip. I remember my uncle working on this type of computer. And it seemed so hard to me back then for me to understand. When I was very young. Now I have worked on much harder things it does not. Just very simple. Still is hard for most people though. :P
those tin plated connectors on the motherboard always looked like a weak design
Effing sexy how you found that bad chip. Earned my sub brotha!
With the 2102 RAM chip being a 1K x 1 device, you actually have 3 banks of 1K bytes of RAM. By jockeying the bad chip around to the highest location (7C00 hex) you could have used the board as a 3K byte board.
Oh! Those are Patreon names scrolling up the screen... I though my new monitor had a 60hz hum bar on the left side. Good to know. Maybe a slow "bottom ticker tape roll" would work better? And no, my name isn't there yet, sadly :O\ Thank you for the video. Very COoL kit'ness. You RoCk!
I managed to get a cromemco z80 in a flea market here, Argentina, I have to make the backplane. I have uploaded a video, if you have any advice I would like your help, because I don't have the erproms and I can't find where to download the BIN files
Wow! I haven't heard of SWTP in decades.
If RAM appears bad I first reseat all socketed IC's, (machined-pin sockets are the only ones I trust,) then I look for power supply voltages on a couple of chips, then I look for clocks and refresh, then I use my laser thermometer and look for hot chips. If I find nothing, only then do I bother with RAM diags. It's quicker to do the other tests first, and RAM tests back then weren't very sophisticated. If I saw a bunch of errors I'd try to identify a hung address decoder bit or I/O buffers. Socketed chips make fixing RAM boards a breeze, slow but a breeze. Fortunately, I have a pretty good stock of old LSI and VLSI support chips to swap them in and out. If the fault is intermittent then a point-source heatgun and freeze mist are in order.
What chip is used for mem on that board? I'l look to see if I have a couple I can send you. The best person to fix antique boards is an antique tech, and I'm in my 70's. :)
Hi Adrian (and other SWTP enthousiasts), can someone help me with what the connector spacing/pitch is ? 3.96mm , 5.08mm ? Thanks in advance
I have a an TRS-80 model 1 and it has video memory issues and I was wondering if I could stack the chips to fix the video issues. I don't have the skills or knowledge that you have to figure out which chip(s) is bad. Would stacking fix it? Thanks and keep the videos rolling.
Not all 4K programs use the full 4K space. There are plenty of games for the ZX81 that state 16K, but they only use about 4K. (the unexpanded ZX81 is only 1K so you need the 16K RAM expantion). If you leave the last location block empty, there might be enough memory to run some software. :)
Yes, I expanded the ZX81 to 8 KB (four 6116 chips + an LS138 decoder). That was sure enough for some "16K" programs. The key may sometimes even be a inflated (or non shrunk) display file, which happens at around 3.75 K RAM installed iirc (due to the ROM program's design).
@@herrbonk3635 I replaced the 1K RAM with a 16K RAM chip in my 81 a couple of years ago. It's easy. There is a guide on Gadget UK's YT channel.
@@frankowalker4662 I guess you mean a standard 32K SRAM like 62256, but sure. They didn't exist in 1982 though, when I did it ;)
(16 Kbyte SRAM chips are extremely uncommon, afaik. After the late 1970s, standard sizes are 2K, 8K, 32K, 128K, 512K for byte wide ICs.)
@@herrbonk3635 Your probebly right about it being 32K. And yes, if they did exist in 1982, everyone would have been doing it. :)
I Used my old 4K bank with the Fastest RAM I could Get at the Time..I use it for the TSR Programs...
Are you referring to the Motorola D-2 kit? With help from a engineer friend I built a 6800 computer using the D-2 Kit back in 1979.
I am ignorant of vintage computers, however I'm digging this series.
oooh! this was cool! I started using computers only in 1982 -- pretty much when the speccy came out, and it's _so_ cool to learn about computers before that!
Just remember that computers far more advanced than the ZX (or VIC) line existed before this machine was built. (The Xerox Alto of 1972 for instance, which became the inspiration for both Apple Lisa/Mac, M$ Windows and most graphical UNIX shells of the 1980s.)
I love older computers. I hope to see more. Right now I'm trying to get my hands on 2 or 3 special systems. compupro 8/16. And hopefully post a video. But trying to find someone that would be willing to donate one is impossible....
Very cool. CPU cache chips off an old 486/586 motherboard make excellent SRAM boards.
I just remembered this little tide bit if you are programming the 6820, paralllel chip there was a bug that caused data corruption. The bug was fixed when 6821 came out. For the 6820 you had to do a reset before writing to a register.
Excusme sir, you forget use gloves. Thanks for your AWESOME WORK!!!
i recently saw a double floppy disk unit of the swtpc in the exact same design and case (would guess it was 2 8 inch side by side). it was just one picture on the internet, sadly i forgot the URL. Still thought might be worth mentioning
Great detective job Adrian, i was watching this up to 1am in bed lol. So, sleep time as tomorrow on Monday. Have a nice week.
Superb. Love your video! Thank you for your content.
Looks like that code for the ram test is quadratic, especially if it takes more than double the time for double the ram. If you can run that 1k test 4 times, you'll come out ahead, instead of doing the 4k test.
Very cool! I got into computing in the early 80s, and I always wondered how one interacted with machines like this.
I have enjoyed seeing your process and this very old computer come back to life. I hope you can come up with a replacement for the bad chip - it would be great to see the machine maxed in memory.
So if both this machine and the CoCo are based off Motorola's reference design, does that mean it could be modified to run CoCo software? Obviously you would need to make a card that adds video and sound.
6264 8k ram on chip. And used to complain about slow serial port on 8085 as it was in software!
I would have just pressed down on each chip to start with you tend to find with time they magically work there way out of there sockets. If that didn't work then I would have popped each one out and refitted. I don't think I have ever need to use dexoit. Anyway great to see an old machine coming to life.
Just wanted to say I love your videos, you are the one who inspired me to open an old VIC-20 I had and attempt to fix it.
Adrian, your content is great but how about a 5 minute walk though of your personal collection?
Anyone else not convinced that BFD stands for "Basic Floppy Disk?"
I'm enjoying this series so much!
So break the video into 2 smaller parts but publish them at the same time. Then those of us who like longer ones can play them one after another - those who don't can watch the two parts at different times.
2102 rang a bell with me ... Just found 18 of them, been stored for years so there should be at least 1 good one. Where do I send them?
Got quite a few Motorola 6800 series chips as well ...
Have you got the clock chip. Trying to drive the 6800 was a real pain using ttl
@@johnbullpit9481 The MC6871A 1.000MHz MPU Clock?
Yep! Got a few of them ...
That Liberty Electronics terminal would pair nicely with this beast.
mr adrian basement have you tried mounting your camera higher to capture more (wider) of the work bench?
13:12 This is very cool... I think I'll get a nerdgasm. ;-)
What about a new channel with all the videos longform, I know I would watch!!
Figured there'd be quite a few benefits to using a modern computer as a dumb terminal, but loading programs wasn't one I figured.
the 1771 FDC chip isn't that the same as Tandy Model 1 expansion chassis?
Love these videos! Reminds me of the good old days of using debug to run programs on cards.
Damn I like the aesthetic of the single sided pcbs on a dummy board essentially
It's like running an Apple ][ from the system monitor...
@ 31:31, Page 7 of the manual, it indicates which ram chip covers what region/bit of ram.
im surprised anyone bought such a PC, its not exactly user friendly is it ? .. . you need a science degree to understand it. it seems more or less useless for a home user .. What you meant to do with it ? .. or maybe im missing the point ?
But can you play DOOM on it? cool old machine, probably a few months older than me
I love these videos, they are my equivalent of whale song (in a good way)
Can you not find one of these 1k SRAMs now?
Thank you! I really enjoyed this. Love the troubleshooting.
It is interesting how viewers lose interest on longer videos. I've seen this with my antique refrigeration repair videos as well.
This computer is really cool... just never seen anything like it!
I can remember when small computers were all like this ...