my understanding of MTRR (Memory Type Range Registers), is: they are used to "control" access to the 4GB address space of Intel PPro Compatible or better processor, how does this thing really implelmented and does it affect the performance of the OS substantially?
Posted on 2004-02-28 05:20:46 by Pinczakko
I have not checked into this issue yet for my OS, but i do know that Menuet OS is using some MTTR stuff to speed up video access ... so maybe you can deduct something from its sourcecode...
Posted on 2004-02-28 06:34:01 by BogdanOntanu
I found this

On Intel P6 family processors (Pentium Pro, Pentium II and later)
the Memory Type Range Registers (MTRRs) 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.

I have the book "The indispensable PC Hardware book" of
Hans-Peter Messmer and it is a very useful source of

Posted on 2004-04-26 10:56:41 by Opcode
Yes, which is also the common problem for new linux users who attempt to configure the kernel themselves. They complain about AGP Vid Card performance and the first response they get is "did you add MTRR support"?

That is your main use of the MTRR. There are plenty of more uses, it is really up to your "taste" ;)
Posted on 2004-04-26 15:14:14 by SpooK