Get PC BIOS back on UEFI only system

The two reasons I can think of: to run legacy or educational operating systems. There are going to be limitations to what can be supported, but simply getting the OS to boot is part of the battle. It would also be useful for those who want to experiment with operating systems by creating their own. Yes you can do that without BIOS support, but there are many old tutorials floating around that depend upon BIOS support. The BIOS was also created as a primitive hardware compatibility layer, so it will provide basic support for things like I/O.

Re: Get PC BIOS back on UEFI only system

#7

Post by LukeShu » Mon, May 26, 2025, 10:32 PM UTC

Very cool hack.

But, as okanat says, if the goal is to run legacy operating systems, then modern hardware is going to be challenging in other ways too. IME the biggest thing I want PC BIOS back for is the ability to use non-GPT disk layouts, which this doesn't accomplish as, as to use it you put it on the EFI partition on your GPT disk.

Re: Get PC BIOS back on UEFI only system

#8

Post by mmastrac » Mon, May 26, 2025, 10:45 PM UTC

> Windows XP/7's video modesetting logic is a bit mysterious. It may try to set a incompatible mode using int10h, which will cause flickering or even black screen after transferring control to the legacy OS.

I would really love to know more about this.

I assume it's this VGA driver:

https://github.com/tongzx/nt5src/tree/master/Source/XPSP1/NT...

Re: Get PC BIOS back on UEFI only system

#9

Post by axiolite » Mon, May 26, 2025, 10:46 PM UTC

ehutch79 wrote: post #2

Why?

From the project page: "Boot FreeDOS, Windows XP, and Windows 7"

Additionally, it was just 3 years ago that memtest86plus finally got a UEFI version. That was painful for a few years there. (Though the 4GB RAM limit would have made this not an ideal solution.)

I'm sure there are other such self-hosting utilities that haven't been and may not be ported/rewritten to work under UEFI.

Re: Get PC BIOS back on UEFI only system

#10

Post by ronsor » Mon, May 26, 2025, 10:59 PM UTC

mmastrac wrote: post #8

> Windows XP/7's video modesetting logic is a bit mysterious. It may try to set a incompatible mode using int10h, which will cause flickering or even black screen after transferring control to the legacy OS. I would really love to know more about this. I assume it's this VGA driver: https://github.com/tongzx/nt5src/tree/master/Source/XPSP1/NT...

Wow, Microsoft open-sourced Windows XP?