[LinuxBIOS] Problems with Filo booting - HELP

joe at smittys.pointclark.net joe at smittys.pointclark.net
Sat Oct 6 16:39:00 CEST 2007

>> Okay, this is mostly a shot in the dark, but it's the only thing I can
>> find that might cause something like this. I'm looking at the AGP size
>> register (APSIZE, 0xb4) in the datasheet, and the default value is 0x00,
>> which is 256MB (!!). I also don't see anywhere that AGP has to be
>> explicitly enabled, it looks like it's enabled by default (yes, I see
>> AGPCMD, but it says cycles will be ignored, not that the device is
>> actually disabled and freeing the aperture memory).
>> Long story short, try setting the AGP aperture to 32MB and moving the
>> aperture base (APBASE, 0x10-13) to somewhere else, preferably wherever
>> the stock bios moves it to. Even if it's not the root cause, it'll get
>> it out of the way for later.
>> -Corey
Corey, After scatching my head for days (hair thinning even more) I  
think you may be onto something. I have tried changing the values in  
APBASE before with no luck and I think this is why:

1. APSIZE Bits[5:3] need to be set first to 111 too allow APBASE  
Bits[27:25] to become R/W.

2. Now we can set APBASE Bits[27:25] to 111 for 32MB Aperture.

3. I noticed this in my bootlogs:

    PCI: 00:00.0 register 10(00000008), read-only ignoring it

    Which is the APBASE register. I think LB is tring to configure an  
address range for it but not able to because the address range is set  
to read only.

4. Set register GCC0 Bit 9 to 1. This enables access to the Aperture  
allowing LB to configure an address range.

I wish there was a way to just disable the Aperture all togethor for  
now but the i82830 is not designed to run in headless mode (no  
graphics). I will try this out and report back.

Thanks - Joe

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