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.
- K6-2 with 'stepping 12' (do a cat /proc/cpuinfo) supports MTRR.