Setting up MTRR for X11 or mga_vid: =================================== 1. find the base address ~~~~~~~~~~~~~~~~~~~~~~~~ You have 3 cases to find it: - from X11 startup messages, for example: (--) SVGA: PCI: Matrox MGA G400 AGP rev 4, Memory @ 0xd8000000, 0xd4000000 (--) SVGA: Linear framebuffer at 0xD8000000 - from /proc/pci (use lspci -v command): 01:00.0 VGA compatible controller: Matrox Graphics, Inc.: Unknown device 0525 Memory at d8000000 (32-bit, prefetchable) - from mga_vid kernel driver messages (use dmesg): mga_mem_base = d8000000 2. find memory size ~~~~~~~~~~~~~~~~~~~ This is much easier, just convert video ram size to hexadecimal, or use this table: 1 MB 0x100000 2 MB 0x200000 4 MB 0x400000 8 MB 0x800000 16 MB 0x1000000 32 MB 0x2000000 3. setting up mtrr ~~~~~~~~~~~~~~~~~~ You know base address and memory size, let's setup mtrr registers! For example, for the matrox card above (base=0xd8000000) with 32MB ram (size=0x2000000) just execute: echo "base=0xd8000000 size=0x2000000 type=write-combining" >| /proc/mtrr (older K6-2's [around 266Mhz, stepping 0] may not support MTRR.)