Allocateing resouces for PCI expansion roms... (was 440bx VGA probs)

Richard Smith rsmith at
Wed Sep 8 18:16:01 CEST 2004

Adam Sulmicki wrote:

> this obviously assumes non-integrated vga bios. On SiS 650 (IIRC) the VGA
> BIOS would be on the same chip as PC BIOS

Thats the way the Bitworks board works as well.  We have the vbios 
included the LB image because our video chips are on board.  But if you 
are trying to debug things and try other video cards via a slot its a 
real pain.  I end up with like 6 or 7 different flash chips that I have 
to plug in depending on what video card I am trying to mess with.

> I assume LB would do all copying? 

Yes. That way ADLO dosen't have to care about the shadowing.  I'll 
probally ifdef out all the the shadow copy stuff from loader.s when LB 
can handle the vbios shadow since it already does PIRQ.

Not really sure how I'll handle the vbios-in-system-image yet but 
something similar exists with the vbios via real mode IDT code.

> IIRC ADLO would turn off write access
> once copying it was done. The " E) shadow - OFF (write)" Not sure if
> that's strictly necessary but it does happen after the copy operation.

Yeah you RC. Thats the way it works.  The off isn't strictly necessary. 
I ran for about 6 months before I realized I wasn't turning write access 
to that range back off.  As long as no stray process goes plowing 
through that range it dosen't matter.  Of course if that happens you 
have other problems.

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