I recently upgraded my memory from pqi Turbo 4200 DDR2 at 533mhz to Corsair XMS2 DDR2 6400 at 800mhz. Can I "dumb down" the corsair to run with the pqi and give me four gigs? I would think yes except that the timings are way off the pqi is at 3-3-3-8 and the corsair is at 5-5-5-12.
side note: I bought two more sticks today with the same model number something like
CORSAIR TWIN2X2048-6400 R
my current sticks say
CORSAIR TWIN2X2048-6400 G
so is there a difference between "G" and "R"???
In the case of mixed parts, your computer will default to the lowest/slowest common denominator for speeds and timings. So mixing DDR2 667 and DDR2 800 parts will get you more 667 (speed), running at the slower timings of the 800 parts in exchange for the extra capacity. Also, if your computer doesn't do it by itself, you'll need to set the Command Rate to 2T when running 4 sticks. You can possibly get away with tightening the timings in the 800 to run like the 667 stuff (probably - you may need to increase voltage very slightly). But setting 667 stuff to run at 800 will likely result in an unbootable system because the 667 isn't rated to run that fast.