Hi and good evening!

I'm not sure if I can help, but I think I understand what you're looking for;
a free BIOS for an IBM 5170 emulation.

Personally, I think that's an fascinating idea!

However, the "problem" might be that the IBM AT wasn't cloned as often 1:1 like the IBM PC.
The AT quickly got integration and chipsets, which required custom BIOS versions.

That being said, there were alternate BIOSes compatible with the IBM 5170.

Some can be found at minuszerodegrees site under "Images of BIOS ROM's for
IBM 5150/5155/5160/5162/5170".

Alternatively, there's at least another way to get hands on an AT compatible BIOS.
Some emulators, like SoftPC/SoftAT (Mac) had a very bare bone AT BIOS, if memory serves.

It might be possible to dump it via debug etc. inside a DOS "VM".
That way, you had something to experiment with.
It's not ideal, sure. But it's a start. Good luck.

Best regards,
Jo22

Hi!

Thanks for your answer, and for the links.
Make sense that there are no opensource ones done if AT/286 machines (to a large extent) utilizes integrated chipsets.

Guess I will build and test the emulator with IBM's proprietary BIOSes for now then.

Perhaps it would be an option to extend the Super PC/Turbo XT BIOS for AT machines in the long run? Not sure how much work that would be?
I do have a copy of Phoenix technical reference series. 😁
I would relay like to ship my emulator with 100% opensource code.

Hi again! 🙂

I'm sorry that I couldn't be more helpful.
Maybe there are other people seeing this thread and have some ideas, too.
- Both Vogons and vcfed.org have some really competent members IMHO.

While I was a 286er user for a longer time (in the 90s), my knowledge isn't complete.
I'm also mainly a user and just a little bit of a programmer myself.
So it's likely that there are some early AT computers or BIOSes I haven't heard of yet.

Also worth a looks might be some late XT BIOSes.
They may not have all the AT specific additions yet, but perhaps can be adapted for the AT's peculiarities (second DMA, IRQ controller, int15h Extended Memory functions etc).

By the way, that reminds me of an older PC emulator that *I think* used its own BIOS code at some point for some of its emulated machines.

https://www.zophar.net/pc/script-pc.html

Maybe its BIOS is helpful to develop some AT style BIOS, not sure.
I also don't remember if it was available as source code. It's been so long I tinkered with it.
You may need wayback machine to retrieve files from the author's site, not sure.

That being said, I wish you good luck! 🙂👍

Jo22

Hi Phix, what's new?

I can't make any promises, but I'll try to find some generic BIOSes in my free time.
- I'll send you a PM if I find something.
Hope that's okay. 🙂

And please don't let anyone disencourage you.

Your idea is neat, I think. The AT was equally important as the PC/XT, I think.

I'd really love to see an open emulation of an AT or XT286 type of PC one day!

Best regards,
Jo22

Hi!

Thanks!
That would be very helpful. But the main point for me is that it has be be freely distributable. (Preferably open-source.)

I created a branch here. Where I have added some AT experiments. Currently I'm testing some A20 stuff.
But writing a full AT BIOS is going to be a lot of work. 😁

For further development of my emulator I'm testing with the IBM AT BIOS from 1984.