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:
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?
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. -Andi