Depends, most RAM does run synchronously. There are different memory dividers you can mess with so memory is running fast but asynchronously.
Intel's bus speeds are on a quad pumped bus. What that means is that a 400MHZ Intel bus is really 100MHZ, 800MHZ is 200MHZ in reality.
Getting a new 2.4C is a good call because not only can you OC the hell out of it, but it has hyperthreading which tricks the OS (assuming you have XP or 2K) into thinking its a multiprocessor system. Pretty nice when you're able to do 2-3 solid CPU intensive tasks at once with no slowdowns.
2ghz+ celerons are the only ones based on the northwood core. The other problem is that they have less on-die (CPU) cache... which cripples them.
P4 2.6C, Thermalright SP94/Panaflo 92MM M1A, IC7 Max3, Swifty MCX159, 1GB Geil PC4000 Ultra Plat, Radeon 8500, Audigy 2, 2X WD Raptor RAID 0, WD 250GB SE, Plex 708A, 166SDVD, LianLi PC75, XP Pro.