[LinuxBIOS] MB1030 / 3036 I like 13 :D

Richard Smith smithbone at gmail.com
Wed Apr 26 18:42:20 CEST 2006

On 4/26/06, Christian Sühs <chris at suehsi.de> wrote:
> >
> >
> > No, different reason. I guess the ram at 0xc0000 is not visible or
> > writable. The datasheet usually knows how to make that area writable.
> >
> Datasheet of which part ??
> I have them all :D

I bet access to your video bios cache area is still write protected. 
Look for something in the CPU or northbridge datasheets (usually
northbrdge but the Geode is a bit wierd) that talks about controlling
reads and writes to this range.  A lot of times its called the c000

Ah... Nevermind... I just pulled the datasheet.  According to what I
read I dont think you have a vbios cache.  Page 94 Section 3.5.3 ROM

The CS5530A positively decodes memory addresses
000F0000h-000FFFFFh (64 KB) and FFFC0000h-
FFFFFFFFh (256 KB) at reset. These memory cycles
cause the CS5530A to claim the cycle, and generate an
ISA bus memory cycle with KBROMCS# asserted.

I don't see anywhere that you can enable this section as read from
ROM/ write to RAM like you would do for a normal vbios shadow.   You
can disable the area completely but not on a  partial read/write

If this is true then if you can't see your vbios show up at 0xfffc0000
then its not in your ROM image correctly.

This would explain why the user space emulator works but the in-tree dosent.

Richard A. Smith

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