Comment 13 for bug 314928

When you've found the line that works best for your system you could add it to /etc/rc.local

In my case:
#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.
echo "base=0xe0000000 size=0x10000000 type=write-combining" > /proc/mtrr
exit 0