What's MTRR mapping?

[CitizenInsomniac]

My Asus A8V-E Deluxe BIOS has a DRAM configuration option called "MTRR mapping mode". Available options are "Continuous" (default) and "Discrete". The setting isn't documented in the manual and the only explanation offered by the BIOS says that "Discrete mode is a more agressive mapping mode". Doesn't that translate to "better peformance"? What exactly is it?

 

[Eva_Unit_0]

I've wondered that myself...my AX8 has the same bios setting. I've never dared change it lol.

Well after some googling I found that apparently changing that setting can fix issues with how much memory is read by an operating system. (like if you have 4 gigs and it's only being read as 3 gigs...I've heard of that issue being fairly common) But I don't know what it actually does for performance.