"Double sided" RAM has its chips divided into two sides (called "banks"), only one of which can be seen at a time by the computer. Initially, these were created by essentially attaching two single-sided SIMM cards to the same PCB, but more modern chips use different wiring. Pins 33 and 45 on the board are used by double-sided memory, and can sometimes be an indicator as to whether a given module is single or double-sided. To use the second half of the storage available, the computer must switch to the second bank, and can no longer read or write to the first half until it switches back again.
Higher-end computer systems may wish to avoid using double-sided memory because of the reduced performance that results from the time needed to switch banks, however it is not a noticeable decrease for the majority of personal uses.
lol ctrl-c + ctrl-v off wikipedia....
CPU: Intel Q6600 Quad @ 2.4 Ghz per core
Motherboard: ASUS P5B-Deluxe wifi
Hardrives: IDE MAXTOR 80 Gb (Windows)
2x SATA MAXTOR 320 Gbs in raid
Video Card: Nvidia 8800GTS (revised 512mb)
RAM: 6 Gb 667 kingston dual channel
Monitor: ASUS VW192T
Mouse: Microsoft Habu
Power Supply: Topower 1000W
OS: Windows XP x64 edition (to support all ma ram :D)