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I patched Bochs to control the A20 line via the bochsrc file
Posted: Thu Oct 08, 2026 11:06 am
by OSCASSEMBLY
I patched Bochs so we can control the state of the A20 line via the bochsrc file in a BIOS-independent way.
I made that for me and it turned out to be really helpful.
So you may find it useful too.
Here is my fork on Github:
https://github.com/wewauction-create/Bochs_A20
Take care 1337 fellow
Re: I patched Bochs to control the A20 line via the bochsrc file
Posted: Fri Oct 09, 2026 12:11 pm
by Octocontrabass
Wouldn't it make more sense to patch the Bochs BIOS rather than Bochs itself?
Re: I patched Bochs to control the A20 line via the bochsrc file
Posted: Fri Oct 09, 2026 12:16 pm
by OSCASSEMBLY
Octocontrabass wrote: ↑Fri Oct 09, 2026 12:11 pm
Wouldn't it make more sense to patch the Bochs BIOS rather than Bochs itself?
I said I made that because I wanted a BIOS-independent way of controlling the A20 line.
What if someone wants to use a BIOS that he doesn't have access to it's source code, and it enables the A20 line?
Re: I patched Bochs to control the A20 line via the bochsrc file
Posted: Fri Oct 09, 2026 12:39 pm
by Octocontrabass
OSCASSEMBLY wrote: ↑Fri Oct 09, 2026 12:16 pmWhat if someone wants to use a BIOS that he doesn't have access to it's source code, and it enables the A20 line?
Does Bochs support any closed-source BIOSes?
Re: I patched Bochs to control the A20 line via the bochsrc file
Posted: Fri Oct 09, 2026 12:46 pm
by BenLunt
Octocontrabass wrote: ↑Fri Oct 09, 2026 12:11 pm
Wouldn't it make more sense to patch the Bochs BIOS rather than Bochs itself?
This has been discussed before:
https://github.com/bochs-emu/Bochs/pull/911
When I get a chance, I may be able to patch
https://github.com/fysnet/i440fx and the make_cmos_image.cc file to do just that. I can look at the standard BIOS included with Bochs, as well.
The idea is a good idea, though I agree, it should be in the BIOS, not in the Bochs tree.
Re: I patched Bochs to control the A20 line via the bochsrc file
Posted: Fri Oct 09, 2026 2:44 pm
by OSCASSEMBLY
Guys it won't hurt
I just thought that it is a good idea to share it
Besides, yes, Bochs support a lot of BIOSes. Some of them are closed source perhaps.
Re: I patched Bochs to control the A20 line via the bochsrc file
Posted: Fri Oct 09, 2026 2:46 pm
by OSCASSEMBLY
BenLunt wrote: ↑Fri Oct 09, 2026 12:46 pm
Octocontrabass wrote: ↑Fri Oct 09, 2026 12:11 pm
Wouldn't it make more sense to patch the Bochs BIOS rather than Bochs itself?
This has been discussed before:
https://github.com/bochs-emu/Bochs/pull/911
When I get a chance, I may be able to patch
https://github.com/fysnet/i440fx and the make_cmos_image.cc file to do just that. I can look at the standard BIOS included with Bochs, as well.
The idea is a good idea, though I agree, it should be in the BIOS, not in the Bochs tree.
Yeah I am the author of that PR