This memory setting refers to the 'command rate' of 1T(one clock cycle) or 2T(two clock cycles). As in most memory timings, smaller is faster/better, but if 1T is causing instability and data loss or corruption, you may have to fall back to 2T. This is particularly true if you are operating at high OC memory frequencies.
P4P800E-D:~:P4 3.0C@3.75GHz:~:Zal7000AlCu:~:OCZ4001024ELDCPER2-K@250MHz 2.5-3-3-7
WinXP SP2>2X160GB Samsung SATA ICH5R RAID1:~:2x80GB Samsung SATA Promise RAID0
ATI A-I-W X800XT~SB Audigy2 ZS~2X BenQ1620~Antec SLK3700AMB~Antec SmartPower2.0 500W