UncleMacro

The higher the clock rate, the noisier the RAM bus is. So in a single RAM channel motherboard (64 bits wide) like a KV7, it's common to support only two DIMMs at high speeds and three DIMMs at low speeds. A dual RAM channel motherboard (128 bits wide) which supports four DIMMs is only actually putting two DIMMs on each of its two channels. Putting three DIMMs on a RAM channel tends to be flakey at high speeds. I have two 1GB sticks running in a KV7 just fine. I don't think I'd try running three sticks at a lower speed. Even at lower clock speeds, three DDR DIMMs per RAM channel can be difficult to get stable sometimes.