Mailinglist Archive: opensuse-amd64 (126 mails)

[John McCorquodale <mcq1@xxxxxxxxxxxxxxxxxxxx>]

In a previous message, I mentioned the strange MTRR setup (which seems to be
coming from BIOS?) on the Tyan S2885:

>   linux:~ # cat /proc/mtrr
>   reg00: base=0xc0000000 (3072MB), size=1024MB: uncachable, count=1
>   reg01: base=0xbe000000 (3040MB), size=  32MB: uncachable, count=1

If I erase reg00 and replace it with three others:

  0xc0000000 size=256MB
  0xd8000000 size=128MB
  0xe0000000 size=512MB

all uncachable, I've effectively removed the MTRR from the PCI physical
addresses on which my video card's framebuffer memory sits.  I can then add
a write-combining MTRR:

  0xd0000000 size=128MB

And things don't speed up.  No surprise, since something is broken.  The
surprise is that my system proceeds to quickly crash!  Why on earth would
this blow my system away?  There shouldn't be anything at d0000000-d7ffffff
except framebuffer memory, which might garbage my screen (I'm in text mode)
but shouldn't cause spewage indicating vast memory corruption followed quickly
by a crash...should it?

Am I missing something important about How It All Works?

Thanks,

-mcq