A Bit on Extreme Memory Profile
First off, before we get onto the OCZ memory modules themselves we wanted to give a bit of a run down on what the Extreme Memory Profile (or XMP as we will be calling it from now on) does.
Extreme Memory Profiles are basically Intel's own version of NVIDIA's EPP memory technology that was introduced into the DDR2 memory line for their own 600 series chipsets for both AMD and Intel, as well as the 590 SLI chipset for AMD. Basically, what we are talking about is an extension of the standard SPD timing system that has been used since the original SDRAM.
SPD is a non-violate EEPROM memory chip that is on all SDRAM based memory modules (this includes DDR, DDR2 and DDR3) which tells the motherboard what timings the modules are designed to run at and allows the board to configure the BIOS accordingly to what the modules are. When you mix and match different speed modules, the SPD system slows the entire lot down to the slowest module's specs; so if you place a DDR3 1066 and a DDR3 1333 module into the board that are both the same size, if the 1066MHz module can't handle 1333MHz according to SPD info, the 1333MHz module is slowed down and run at the same timings as the 1066MHz module.
XMP is a second set of instructions that act as an overclocking guide for the system with advanced timing function, if you want to run the modules at tighter timings you can set a turbo option in the BIOS to allow this and the modules are run at an extra set of enhanced timings that increase the performance but also limit the overclocking if you choose to use them. Also included in the XMP setup is additional voltage options depending on what profile you choose.
For instance, if you decide to use the modules at their highest memory clock and decide to go for the tightest timings possible, the modules will reduce CAS latencies across the board; but to cope with the increased demand the voltage is automatically raised by sending the chipset a special XMP signal that tells the DIMM voltage regulator to increase memory voltage to a pre-set limit as defined by the profile used.
XMP based memory will only come in the form of DDR3 modules and X38 and X48 chipsets. DDR2 based X38 will not have this feature, Intel is going all out on DDR3 here and SLI certified DDR3 with its EPP will not run XMP, so make sure it's Intel XMP Certified if you want to use this new feature, and be sure to get a X38 or upcoming X48 board to take advantage.