htt is used to determine the cpu's clock speed. the 3500+ winchester has a default multiplier of 11 (200httx11=2200mhz). now, ram speed is calculated down from the cpu clock speed. running 1:1 or as the neo2 bios puts it "200" will match your memory frequency to the htt frequency, but running any of the other memory settings will set your memory frequency based upon a divider from the cpu clock.
since you say you've tested your ram to 250, you can try running 11x250 and use prime95 or superpi to test for stability. i usually test superpi first. if it finishes one iteration of 32mm superpi, then i'll begin to prime it for at least 6-8 hours. if you want to use a 3dmark to test stability, you need to use 3dmark01 since it is more cpu dependent than the other 3dmarks.
if you want to use a high htt frequency then you'll most likely need to use the dividers for your memory frequency. when you change the htt frequency, it's best to use 4x for anything up to 250, and 3x for anything up to 300 and so on. you don't want your htt to go over 1000 (htt x htt multi), as it can cause unneeded instablity.
if i missed anything, be sure to ask, and if i dont answer in time, i'm sure someone else will.
