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80386DX ISA single board microcomputer

alexandrugroza.ro

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Re: 80386DX ISA single board microcomputer

#41

Post by oso2k »

mahoro wrote: post #37

This is absolutely amazing and beautiful work. Congratulations to Alexandru! BTW can someone clarify what's the benefits of building the computer as an ISA board?

ISA boards (main, backplane and/or add-on) are relatively simple to design and interface. Not having to worry about north bridge and south bridge chips, PnP, PCI, AGP, VLB, EISA, MCA, etc. makes designs simpler. Many of the period correct sound card chips, VGA chips, Ethernet chips, serial and parallel chips are still available to design around.

https://github.com/skiselev/isa8_backplane

Re: 80386DX ISA single board microcomputer

#42

Post by flyinglizard »

guerrilla wrote: post #34
flyinglizard wrote: post #7

Awesome project, although I personally can’t identify with putting such effort into reinventing the past instead of making something new. I suspect different people live in different periods. I’ve known people who always dwell on the past, those who are preoccupied with the future and those who are in the present and not overthink too much in either direction.

Because it's possible. Bringing up more advanced CPUs alone and with hobbyist tools is borderline impossible. Nothing revolutionary changed (Sorry Pentiums) until the Opteron, so you're covering an entie era by doing this and learning a ton that applies even today. I dislike the premise of your question though. There's no reason it need to be economically useful. People can just do things thy love and enjoy. On top o…

The level of expertise in the OP is way above “walking” when translated to EE terms. It’s educational no doubt but so was every one of my professional projects over the years.

Yes I completely agree that people should do what they enjoy - it’s just that every now and then I see this completely amazing undertaking with absolutely no extrinsic value and I wonder. It’s all a very personal vantage point of course.

Re: 80386DX ISA single board microcomputer

#44

Post by kar1181 »

I wish I had more upvotes to give for this. I started wondering (completely naively) how hard would it be to just go ahead and design a motherboard for an old x86 CPU from scratch.

Impossibly hard, though clearly not for everyone. What an incredible effort.

Re: 80386DX ISA single board microcomputer

#45

Post by flyinglizard »

jtl999 wrote: post #17
anyfoo wrote: post #8

Earlier quoted context omitted.

A lot can be learned for the present from such projects. Older stuff is usually less integrated, more tolerant to manufacturing by hand (for many reasons, including relatively easy to deal with frequencies, board layout, and required layers), and you have plenty of "reference" implementation and documentation to delve into. It is a very valuable hands-on experience that certainly gives an edge over people who only kn…

I guess the idea is if you're studying EE and related fields: "crawl before you can walk"

This is not crawling by any stretch of imagination. It’s low speed digital which is the only thing making it “easy”, other than that it’s worlds apart in complexity from a reasonable educational or DIY project.

Re: 80386DX ISA single board microcomputer

#46

Post by guerrilla »

gruturo wrote: post #38
ahefner wrote: post #5

Earlier quoted context omitted.

How so? SX was always the crappy version.

True, but SX used to stand (officially? dunno) for Singleword Xchange, as it had a 16 bit bus. DX was Doubleword Xchange, hence 32bit bus. Then in the 486, the bus was always 32-bit (at least from Intel. I have a faint memory of Cyrix 486SLCs with a 16bit bus), and now the SX-DX indicated the presence of an integrated FPU instead. Bonus: the 80487 was not just an FPU. It was a full 486DX which just disabled the main…

> Singleword Xchange > Doubleword Xchange

Thank you! I knew all the difference (the same as 8088 vs. 8086) but never knew why those names were used. I love these tidbits of history.

Re: 80386DX ISA single board microcomputer

#47

Post by 123pie123 »

These things remind me of one of my first jobs as a bench engineer 'trying' to fix PCs

the vast majority of problems back then was the power supply and the vast majority of the issues with power supplies was burned out capacitors - easily fixable.

for some bizaar reason one memory that also sticks out was the painful compatibility issues of putting seagate hard disks together with conner hard disks (IDE cables) also SCSI was a pita with terminators not working (resistors at the end of the scsi cable).

I built my first PC 386SX (I think it was only a 33MHz - complete with a TURBO button!! :o) ) with bits that other engineers had thrown away - literally, outside they had a skip(dumpster) with 386 motherboards and other stuff they deemed unfixable that I had to keep going through.

everyone was scared of opening monitors - using long screw drivers to ground the tube made them (mostly) safe. I also had to fix a b/w (or technically black/ orange) CGA monitor to go with it. i still managed to get windows running on it.

Re: 80386DX ISA single board microcomputer

#48

Post by guerrilla »

flyinglizard wrote: post #42
guerrilla wrote: post #34

Earlier quoted context omitted.

Because it's possible. Bringing up more advanced CPUs alone and with hobbyist tools is borderline impossible. Nothing revolutionary changed (Sorry Pentiums) until the Opteron, so you're covering an entie era by doing this and learning a ton that applies even today. I dislike the premise of your question though. There's no reason it need to be economically useful. People can just do things thy love and enjoy. On top o…

The level of expertise in the OP is way above “walking” when translated to EE terms. It’s educational no doubt but so was every one of my professional projects over the years. Yes I completely agree that people should do what they enjoy - it’s just that every now and then I see this completely amazing undertaking with absolutely no extrinsic value and I wonder. It’s all a very personal vantage point of course.

> The level of expertise in the OP is way above “walking” when translated to EE terms

I know, I've looked into doing it and this is mind-blowing but they're relative terms and it depends on what you compare it to. This is "walking" compared to bringing up a Ryzen machine.

> with absolutely no extrinsic value

Why should it? And how do you know it doesn't and they just haven't documented that?

Re: 80386DX ISA single board microcomputer

#49

Post by oso2k »

gigel82 wrote: post #30
yitchelle wrote: post #19

It is truly amazing that one person can bring up a 386DX board system. It is true that there are tons of docs available, but still to bring everything together and to get it running is truly amazing. The team size at any of the PC OEMs doing a 386DX design when it was the state of the art would be at least 25 engineers and managers, easily. Congrats to Alexandru for hitting this out of the park.

I've always wondered why no one came up with cheaper / mass produced 386/486 SOCs; are there any still-valid patents preventing that or is it too much work when we have powerful & cheap ARM SOCs that can emulate them...

386, 486 embedded chips were widely produced as SOCs but they’re embedded in places you probably wouldn’t look for them. Which is why they’re SOCs. :) 586 and semi 686 compatibles are still available in certain quantities.

Today, a Pi0W could emulate anything up to a low end 486, Pi0-2W/CM3 could do about 486DX-100/low end Pentium.

https://en.m.wikipedia.org/wiki/List_of_former_IA-32_compati...

https://m.youtube.com/watch?v=8fSdLKx5HlU

https://m.youtube.com/watch?v=6cXdWMOl8QE&t=241s

Re: 80386DX ISA single board microcomputer

#50

Post by unixhero »

123pie123 wrote: post #47

These things remind me of one of my first jobs as a bench engineer 'trying' to fix PCs the vast majority of problems back then was the power supply and the vast majority of the issues with power supplies was burned out capacitors - easily fixable. for some bizaar reason one memory that also sticks out was the painful compatibility issues of putting seagate hard disks together with conner hard disks (IDE cables) also…

Good story!

Everyone were correct about being afraid of opening CRT monitors. Repairing them is a whole other domain than PC electronics. A CRT ZAP from the cathode ray components can kill. That is not a place one should poke around trying to find solutions.

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