1T command is not available for intel or nvidia chipset.
it is only available for VIA chipset. (Idon't know about ALi or SiS)
Eventhough the memory is rated at 2-2-2-6-1, I'm sure it will also work at 2-2-2-3-1 200MHz (DDR 400MHz).. 2-2-2-2-1 is too tough...
Lower setting is always better..
However, you may need raise the timing if you use higher FSB than 200MHz..
Performance difference between 3, 4, 5 and 6 is not that big...