For me It's unnecessarily complex solution.
... I mad a little C programme ...
Just launch System Settings -> Advanced tab -> Autostart -> Add Script -> choose fixmtrr.sh and Run On - Startup
And thats all -- after reboot for assurance I've manually did:
Extracing base address and memory size from lspci -v
Supplying corrected MTRR ranges to /proc/mtrr
doing nothing, MTRR range already set up
reg00: base=0x000000000 ( 0MB), size= 1024MB, count=1: write-back
reg01: base=0x03f800000 ( 1016MB), size= 8MB, count=1: uncachable
reg02: base=0x0d0000000 ( 3328MB), size= 256MB, count=1: write-combining