When your ram is running at a different speed (FSB) than your cpu, your running it asynchronously (async).
Conversly, when they are the same it called synchronous (in sync)
(I've probrably mangled the word with bad spelling)
For AMD, your performance will be better if running (cpu and ram) in sync.
For Intel, running async is OK.
Hope that helps
Barton 2500+
Abit NF7-S v 2.0
Maxtor 60GB ATA 133 7200RPM
512MB Corsair Twinx 3200LL
9600 Pro
Enermax Noisetaker 420 watts
Win98SE