Hes getting a new PC guys, hes asking which ram he should get in it.
The RAM to look for is of course, the one that gives you the best performance. I'll try and put it in layman's terms, and please take into account that what I say below may not be 100% technically accurate, but it gives you the best picture to make a decision!
In RAM, theres 3 things you need to take into account besides price and brand name:
The Mhz the ram runs at.
The Mhz of the front side bus of the motherboard where the ram will plug in
The Front Side Bus capability of the processor you plug into the motherboard.
Think of the Front Side Bus as being a bridge between the Processor (CPU) and the RAM. If the RAM has a 4 lane highway and the bridge is only 2 lanes, you get a bottleneck. The processor also has "lanes" going out of the CPU towards the bridge.
SDRAM has 1 lane bridge.. which was good because computers way back then when this RAM was avaliable, only had 1 lane RAM and 1 lane CPU.
Then came DDR, which is Double Data Rate. Aka, TWO lanes. Motherboards using DDR ram began to come with 2 lane "bridges" (Front Side Bus, aka FSB) accordingly.
It was with DDR that the speed at which data traveled in those lanes began to increase. From 133mhz to 266mhz to 333mhz and now up to 400mhz (latest one).
And then came Rambus Ram (RDRAM), which after a brief stint of sleeping with Intel Corp., offered a FOUR lane RAM that ran at higher speeds than DDR. So accordingly, motherboards began to come with higher FSB "bridges" so that the RDRAM could work well on them. And RDRAM was GOOD , it is GOOD.. but its also $$$$$.
This year however, DDR made a comeback. They made DUAL CHANNEL DDR, which is like having the same four lanes as the RDRAM had, but being dual channel, it makes it run at 800mhz. Accordingly, manufacturers began making motherboards with Dual DDR "bridges", which had 800mhz FSB.
And they are REALLY good, REALLY fast and less $$$ than the slower RDRAM.
BUT! (always a BUT!), for best performance the CPU also has a MHZ rating and it should be higher or match the RAM/Bridge speed. Up until now , that wasnt a problem.
Pentium 4's now run at 533 mhz speed. The latest P4, the 3.0 ghz ones, can come in either 533mhz or 800mhz speeds (speeds to connect the CPU to the bridge that is, dont get confused here! Think of it as the On-Ramp

).
So after all this junk ive posted , here's your choices in my opinion:
For great performance and not so expensive system: Buy a pentium 4 @ 2.66ghz with RDRAM. (the P4 running at 533mhz, same as the RAM).
For performance that beats the above but much cheaper, get an AMD 2.8Ghz with 400mhz DDR. (The AMD can run to 533 mhz and the ram runs at 400mhz, but the AMD's superior chip design beats the P4 in performance).
For THE best of the best , get yourself a P4 3.0ghz 800FSB (aka, CPU has 800mhz front side bus) with the Dual Channel 400mhz DDR RAM.
As I said at the start, the above is not technically accurate.