Memory Type Range Register (MTRR)

On Intel P6 family processors (Pentium Pro, Pentium !II and later) the Memory Type Range Registers (MTRR's) may be used to control processor access to memory ranges. This is most useful when you have a video (VGA) card on a PCI or AGP bus. Enabling write-combining allows bus write transfers to be combined into a larger transfer before bursting over the PCI / AGP bus. This can increase performance of image write operations 2.5 times or more.