From WikiChip
Extreme Memory Profile (XMP) - Intel
Extreme Memory Profile (XMP) is a specification serving as an extension to the standard JEDEC SPD specifications developed by Intel.
Mechanism
Memory DIMMs incorporate a serial presence detect (SPD) chip which contains information about the memory module. This chip follows a specification defined by JEDEC which includes a number of tables, including reserved entries unused. Intel's XMP standard uses the reserved entries in the SPD for its own purpose: particularly for overclocking purpose.
XMP uses the reserved portion of the SPD table for a number of additional features:
- Multiple SPD profiles - Allows for a number of different memory profiles which can be selected depending on the usage; for example for a special low-latency custom profile for gaming.
- Memory vendor specific SPD fields - This gives memory module suppliers the ability to set a number of their own profiles based on the module capabilities.
- Easy Over-clocking (Novice) - Provides users with a number of predefined overclocked profiles that have been determined to be stable. This allows users to selected those predefined profiles instead of adjusting individual parameters in BIOS.
- Advanced Overclocking (Intermediate/Expert Users) - Allows more advanced users to change specific SPD parameters in the BIOS and save those profiles.
- Fail-safe default boot - Allows the ability to restore to one of the usual default JEDEC settings after a bad settings.