OSDev.org

I seem to have found the listing for an original 8086 BIOS machine in this PDF:

ibm5160techref.pdf


Now I know that it doesn't really include the VGA BIOS source code since it's supposed to be in another ROM chip in the graphics card.

Apart from the VGA BIOS from Bochs (which wouldn't matter as much as an original 8086 version), where can I find a ZIP or an ASM file with that source code module so I can inspect the original programming quirks for the original VGA more directly?

As far as I've been able to find, IBM did not publish the source code to the VGA BIOS. If you want to examine it, you'll have to disassemble it yourself.

The 5160 didn't support VGA cards, though some (not all) cards will work with it.

I suspect your only way of getting a ROM listing would be to get a VGA card and inspect the ROM.