Hi,

Do you need DDR400 RAM in order to use a FSB400 CPU or would DDR333 work OK?

If the CPU is running at 200mhz (400FSB) & the RAM is running at 166mhz (DDR333), the RAM becomes the system's bottleneck. Can you run that way? Sure...but if you want optimal performance, your CPU & RAM should run at the same speed.

Asus A7N8X-X
1800+ @8x210mhz
512mb PC3200
Ti4200/8X 128mb
WDC 60GB

DDR333, uses both up and down pulses and is therefore stated as running at 333MHz (hence the name) not 166MHz. But enough tech stuff, the simple answer is you dont need DDR400, DDR333 is fine, you wont really notice any difference between the 2 anyway!

Wizard ICT. Microsoft Certified Professional

We're splitting hairs here...but the clock setting for DDR333 is 166mhz, because of double data rate technology (which you described above) it's "effective" speed is 333mhz

Asus A7N8X-X
1800+ @8x210mhz
512mb PC3200
Ti4200/8X 128mb
WDC 60GB

And it may or may not work reliably at 400Mhz. If it does you've saved a few bucks...if it doesn't you get to go shopping.

Skip

A buddy of mine just built a new box with a Soyo board with a 3200+ Athlon and a gig of generic 333 ddr. It was unstable with 400fsb and he had to run it at 333fsb, however this caused his 3200+ Athlon to run as if he only had 2500+ Athlon.
I built a box with the same motherboard, except I used a 2600+ Athlon (333fsb) and Corsair 512 400 ddr. It runs fine even with some mild overclocking.
I found that the motherboard can run memory faster than the cpu but not the other way around.
It can make a difference what memory you use, including brand.

Why would you run your memory faster than the CPU when you get no performace gain?

-- Always do what you are afraid to do --