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@mihirsevak4456: the schematic is shown in the video around 12:14 timestamp (the circuit you're asking for is in the bottom-left part). It is also available on my GitHub: github.com/sladorsoft/Intel8088OnBreadboard I used 74HCT14 and 74HCT74. The couple of the pull-up resistors are around 10k and the caps are 1uF

Hi @migry ! You are perfectly right. The timings are not up to specs as another viewer had already noticed and commented on here. Yes, that was my mistake as I was more focused on explaining the PIO on a simple example rather than giving enough attention to the Neopixel specs. From my point of view it was more "this is how PIO works - look at this colourful LED as a confirmation" rather than "this is how you drive Neopixels using something called PIO". Of course I should've thought about timings more carefully, or used a different device for output. The specs for WS2812B say that bits need to follow one another immediately (each bit is 1250ns long) and the pause tells them to reset their inputs and listen to the next series of bits coming. The pause in this case needs to be at least 50us.

Hi @JorgeSilva-em8pf! Yes, I saw someone implementing a Manchester code and built a working Ethernet controller. There is plenty of possibilities of using PIO for communication and if I wanted to try them out it would take hundreds of videos ;-) But in the next video I'm going to show how to programme the Pico W to talk to the Internet via Wi-Fi. I hope you find it interesting as well.

Thank you for that. I know it was a long time between the two last videos, but I'm going to try to make my pace a little bit faster ;-)

Sorry to hear that it didn't work for you. Don't even let me start on building it on Ubuntu. The code (or dependencies between the repos) is very often broken and rarely builds. After producing my binaries I tried to update them later on, but there was always a problem with compilation at different stages. It's hard to troubleshoot your problem remotely, but you could check two things: 1) check if this toolchain is in the PATH: run a command line and type "ia16-elf-gcc.exe" and see if it can be found. 2) go to VS Code, press Shift+Ctrl+P and type "select a kit". Choose this option and check if you can see "GCC 6.3.0 ia16-elf" on your list of toolchains. If it's not there, rescan the toolchains (by again pressing Shift+Ctrl+P and typing "scan for kits") - but it will work only if it is in the PATH.

@@SladorSoft Thank you for your answer, the project gcc-ia16 is a mess for someone that does not know it deeply, but I found out that gcc-ia16 is not mantained anymore and the project that should be used todays is build-ia16, I am trying it. If I get a succes in this task, I can send to you a version project that compiles in linux ubuntu, so you can make it available , if you agree with this.

Hi @keiichicom7891! Thanks for that. Yes, my aim is to implement the BIOS to be able to boot DOS on my computer - maybe not this one on the breadboard, but the one I'm building in more recent videos.

init.asm line 127 checks DISK_CTRL_STATUS_BUSY until data is ready. The way PC disk controllers work they receive a command to read one or more sectors and will only give signal when they have at least one full 512-byte sector ready, either with interrupt or by changing status.

I'm sorry @marcrobach7376, because it looks like I didn't explain this well enough and thanks @rasz for clearing this up. So the Pico first reads the whole sector to its own memory, then clears up the "busy" flag, which lets the Intel CPU to read this buffer byte by byte. The Pico has it's own pointer to the next byte to be read in this buffer and each access from the main CPU increases this pointer. Maybe I should have showed the most important parts of the Pico code in the video - sorry for that confusion.

CF is indeed a 16 bit IDE card and can be directly connected to a 16 bit ISA bus with 2 74245 buffers. A 8088 and 80188 have a 8 bit ISA bus, so a XT-IDE ISA card is a solution for a CF card that exists for years as the 8 bit IDE hard disks like Seagate ST351X are very rare. A 80186 and up have a 16 bit ISA bus and can use a CF card directly. CF has a parallel interface and SD a serial interface and there is where the fun starts...

This will take the same amount of time to adapt an xtide to this than doing on pico because xtide talk to isa and here it is direct cpu access. This board is not pc compatible so it require à huge work to rewrite the xtide bios. See how simple it is to code at the 80188 side with just some registers vs ide.

@@freddyvretrozone2849 a 8088 XT does not have hard disk support in it's main bios like a 80286 AT and up have. How different is the connection to this CPU than the connection via the ISA bus on a PC XT? I have to dig deep in my memory concerning DMA and Interrupt controllers...

Thanks a lot @sjococo! Yes, what you said was exactly my point for not using CF. I added this Pico there not only for the SD card access, but also for keyboard, UART and maybe other peripherals later. It's so much simpler doing it with this Pico board rather than adding support for long forgotten CF cards where I'd need to add something in-between to use it on a 8-bit bus. And also, @sjococo mentioned the most important reason in their last paragraph ;-) That's where the fun starts :-)

Thanks @freddyvretrozone2849. Since the beginning, I emphasised that I'm not trying to build a PC compatible, but I do this only for fun and to have a chance to talk about this old technology. Also, the whole point is to write a BIOS myself, not to use anything out there. It's a project I started for fun, that's it :-)

You are perfectly right @Kitsok! This was just a first attempt to test the idea. Surely, the next step is to implement it properly using DMA. And it's going to be a good excuse to look more closely at the timings in both cases using a logic analyser.

Thank you! Yes, I was wondering about it as well... It's hard to estimate, but... are you thinking what I'm thinking? ;-) Maybe at some point in the future, I'll try to emulate 80188 on Pico?

@@SladorSoft that would be awesome tbh but also hard

@@SladorSoft CoreMark 67.181 CoreMark/MHz 1.0179 Inter 486 And pico CoreMark about 260 CoreMark/MHz about 2 Pico 2 Core mark about 600 Core mark/MHz about 4 RISC cores also about 4 Pico 4x st 8xmt Pico2 10x st 20x Mt St-single thread Mt-Multi tread

Oh, thank you @ModSlash. Yes, I had a break, but from now on, I'll try to reserve as much time as I can to make videos more often. I have this problem, where I have more ideas than the time to realise them... ;-)

Thank you very much. I'm really happy that you found it useful!

No I haven't, but there should be no difference in the programme nor the outcome. I ran Fibonacci sequence again, step by step on 8088 and using full 16-bit registers in part 6 of this series th-cam.com/video/8G3bwkIS3do/w-d-xo.html around 13:00 mark.

MS-DOS was written for 8088 CPU, so it is compatible, yes. Obviously, to run MS-DOS you need much more than just a CPU. For example, you need a storage to load MS-DOS from, you need a keyboard controller, a graphics card to display anything on, etc. If you look at my more recent videos, where I build a 80188 system, you will find that I'm working towards this goal - already added a disk controller and more is coming, so please stay tuned!

Hi there! Thanks for watching and here are the answers to your questions: 1) Yes, I'm using 80C88 - any manufacturer would do it. You can find the datasheets on the Internet easily. I show the relevant parts of it in my videos (including the pinout) as well. 2) Any LEDs would work. Since we are using the 5V logic here and an LED usually needs a few mA to light up, the resistors could have values from around 470 Ohms to 2.2k. It depends on the LEDs, so you can experiment. I found my blue ones really bright at a small current, so used the 2.2k with them. Others are 1.2k in my case I think. 3) I showed the schematics around 12:14 mark (the clock and reset circuit is in the left bottom part). Have a look at my GitHub pages where I publish all the schematics as well. I used two ICs: 74HC14 and 74HC74 (both can be HC or HCT). I missed putting the resistor and capacitor values on the schematics - they could be something around 10-47k and 1-10uF respectively. They are only used there to debounce the buttons, so the values may vary.

@@SladorSoft Thanks. I am trying to build this. Will let you know if have any issues.

Don't hesitate to ask, if you need help

@@SladorSoft Thanks for your offer to help. I have ordered the parts online and waiting for them to arrive. Is there an email I can contact you on in case I get stuck? Thanks.

It depends whether you used a crystal oscillator with your 8284, or a button and you clocked it manually. If you used a crystal, the clock would obviously be very fast and the LEDs would blink so quickly, that they would appear all on. If you used a button and generate the clock manually, after 7 ticks from the reset, you would see exactly the same outcome as in the video (around 8:40 mark), so the 16 LEDs would be turned on (in A19 to A4 lines) and the rest 4 (A3 to A0) would be off.

Yes, this and even more is possible. One PIO device has 4 state machines, each of them can run a separate programme and each of them has separate GPIO pin binding, clock divisors, etc. The only limitation is that all 4 state machines (programmes) share the same programme memory, which is only 32-instruction long. In other words, all (up to) four of your programmes need to fit together in this 32-instruction long space. On top of that, there are two completely independent PIOs on RP2040 chip, so you can theoretically run up to 8 short programmes. The example in the video was as simple as possible and was using only one state machine of one PIO. In one of the future videos I'll be showing an example of multiple programmes running on the same PIO.

​@@SladorSoft Ohh, thanks. I'm very interested, but i cant find any easy tutorial. i'm trying to make my own PIO program for WS2812, only works one pixel, i think is a problem with timings, you know any way to send the data to others pixels?

Sorry for my english, i speak spanish.

Thank you! I know exactly what you mean. Memories... ;-)

Obrigado meu amigo! Next video is almost done - I am struggling with finding enough time to finish it. I have plans for at least 3 more videos in this series after which I'm going to design a new, hopefully final PCB for this computer.

Apologies for late response. I assume you're referring to the last example. Please note that the interrupt flag in this programme is used only as a "busy" flag, which the main programme can check before sending new data to PIO over DMA to keep the required "reset" timeout of the LED. It does not stop the main programme from doing something else. In this programme this flag does not even raise a CPU interrupt. I used the while loop only to show how we can use PIO interrupt bits to synchronise the CPU programme with the PIO one. This is just a trivial example not meant to use in any "production" code. In real-life programme you could simply raise a CPU interrupt when the IRQ flag is set, which handler would send the data from RAM to PIO automatically. Then the main programme would write the required pattern data to the RAM and go on doing other stuff.

It is definitely NOT. I shall release next video soon - it requires lots of preparations, but I'm almost done. Any other videos I created recently were related to this series anyway. I made the most recent one, about running FreeRTOS on RPi Pico, because I needed the Pico in my Intel computer as a peripheral, which you will se working very soon. There will be at least three more videos before I create the new, finalised PCB, which I will show you later and start working seriously on its BIOS to get a complete, working computer.

Thanks for surviving the hell ;-) But, more seriously, I'd appreciate if you shared the reasons for you struggling. Too much information (or coding)? Too boring? Not clear enough? What could I do better? Thanks for that!

Stacksmashing also has a fabulous video...

Oh no I see it's even more convoluted than that lol.

Merci beaucoup monsieur ;-)

Hi @yuriiradkovskyi8330. I have no experience with the V20, but I'm afraid that the manual clock may be impossible (despite that it's CMOS as you pointed out). According to its datasheet the maximum allowed clock cycle is 500ns, which translates to the minimum frequency of 2MHz.

@@SladorSoft Thanx, will buy 80C88 then for experiments like that

Thank you @DrJonEA for your comment. I had exactly the same feeling about FreeRTOS when I first saw it, but quickly realised that it's really simple to use. Funny you mentioned PicoW and lwIP, because last year I built a simple contraption using these just for fun. Maybe I'll show it in a future video as it may be a good starting project for people wanting their PicoW to use the Internet very easily. I used lwIP together with mbedTLS for HTTPS.

@@SladorSoft That sounds great. Perhaps we can do a few cross overs between our two channels.