On Mon, Nov 03, 2003 at 02:44:09PM -0800, John McCorquodale wrote:
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:
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:
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?
Most likely the aperture is there and you are messing with the IOMMU mappings.
Does it go away when you boot with iommu=memaper=2 (this will make your system
lose some memory)
Overall it sounds more like hardware/BIOS issues than a Linux problem. I would
recommend to contact Tyan. You could also try a different video card.