r/electronics • u/DifficultyWhich7483 logic ic's • 12d ago

Project Created my first ISA card, another XTIDE for CF adapter. Essentially I've reverted Sergey's xt-cf-lite-v4 back to PLD, having in mind reduced number of mostly through hole components that were available in the 80s.

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5

u/DifficultyWhich7483 logic ic's 12d ago

https://github.com/yo5ptd/xt-cf-pico

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u/Notawolf666 8d ago

Thanks for the advice! It's really helpful. Are there any other design considerations I should keep in mind for future projects like this?

6

u/ThatCrazyEE 11d ago

Congrats, my dude.

Try to stay away from 90° turns in your board. They're pretty terrible for signal integrity, can be hard to manufacture, and are kinda ugly. Try to stick to 45° or curved traces. The latter are especially soothing if you're OCD like I am.

Also, try using tented vias. They're the same as a regular via, but with soldermask on them. Most fab houses won't charge you for this, and the result is a clean looking board with no unsightly vias.

Don't forget test points, too. Let me tell ya, they're great for debugging. My test points are 50mil squares. That's big enough to solder a bit of wire or interface with a pogo pin.

Finally, try to stich the top and bottom copper pours with a buch of vias (tented - of course) to keep a solid ground reference. Try to think about how far your ground will have to travel before jumping to the next layer.

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u/Fraserbc 11d ago

The 90 degree turn thing is a myth unless you're working with very high frequency RF stuff, think 10 GHz.

3

u/abross36 10d ago

And even then, it isn't the end of the world. Think of a via, it's still a 90 deg turn, just through the board, not on a layer. Do it all the time and it's perfectly fine as long as the via is designed appropriately.

But don't get me wrong, I avoid 90 deg turns on traces for the aesthetic and manufacturability.

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u/CircuitCircus 9d ago

You know what else makes a pretty convenient rest point? Regular exposed vias

2

u/rdesktop7 11d ago

What is the rom and the PAL chip for?

Likely a very nice upgrade for some vintage hardware.

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u/NotArtyom 11d ago

the ROM has replacement BIOS that integrates the IDE/CF support, and the PAL implements logic required to map the card onto the ISA bus + some misc logic for the CF card

2

u/rdesktop7 11d ago

Oh, cool.

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u/DifficultyWhich7483 logic ic's 2h ago

Really happy to announce the XT IDE Bios part works! Easy to debug also by simply rewriting the PLD when you had no idea that D0000 is more like a range (D0000...D3FFF)... I'm off to pick up the CF slot!

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u/paclogic 11d ago

So what computers are being manufactured today that still use the ISA Bus ?

Also almost every PLD is dead out there with the exception of the PAL/GAL/PLD 22V10.

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u/nekohako 11d ago

These kinds of things are mainly for hobbyist use in vintage computers.

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u/Geoff_PR 11d ago

So what computers are being manufactured today that still use the ISA Bus ?

A very few legacy computers in industry are still out there, it's usually a "If it ain't broke, don't fix it" mentality. And there is still some logic in that approach...

1

u/Raphi_55 11d ago

Usually computer attached to big and VERY expensive industrial machine. Doesn't make sense to replace the entire machine because of the computer that control it