Question : Problem: Front System Bus?  RAM Mhz?

What is the Front System Bus, and why do I need to know that it runs at 333Mhz?  What is Dual Channel DDR 400 mean? And how does the RAM frequency affect my computer?

Ausus A7N8X2.0
AMD Athalon 3000+
1Gb DDR RAM
nVidia GeForce FX 5900 Ultra
Windows XP Pro
Sound Blaster Audigy 2 Platinum

Answer : Problem: Front System Bus?  RAM Mhz?

There are several different 'Bus' Speeds when referring to your PC.

think of a Bus as a device that information travels on. . .  There's a memory bus, the cpu bus and the system bus.  (There's also an AGP bus, PCI bus, etc., but we won't get into those . . .)

The computers 'system bus' for currently manufactured processors can be one of the following:  100MHz, 133MHz, 166MHz and 200MHz.

The processors themselves however can be 200MHz, 266MHz, 333MHz, 400MHz, 533MHz or 800MHz depending on the make/model of the CPU.

AMD's current cpu's are 'double-pumped' buses, meaning their 'FSB' (front side bus) on their cpu's is 2x that of your computers 'system bus'.   That means that if you're using a 166MHz system bus on your PC, your cpu is, in fact, running a 333MHz FSB.  

Intel is currently using a 'quad-pump' on their cpu's, meaning the FSB's on their cpu's is 4x that of their computers system bus.   A Celeron 2.0GHz, for example, utilizes a 400MHz FSB, but you clock it during the setup of the computer at 20 x 100MHz and the computers system bus runs at 100MHz.   A P4 3.06 is a 533MHz FSB cpu, but the computers system bus is 133MHz.

Confusing, I know. . .  hopefully that explains the cpu vs. system bus speed somewhat.

Your memory bus is another story.  In both AMD and Intel systems the memory bus of DDR systems is double-pumped.  DDR 400, (also called PC3200, fyi) as you mentioned, is memory which can operate at 400MHz speed, but is actually setup on your computer as 200MHz. . .   DDR 333 (also called PC2700) is memory which can operate at 333MHz speed, but is actually setup on your computer as 166MHz.

As far as how RAM frequency affects your computer:  Generally speaking, the faster the memory bus the faster overall performance of the system.  However it should be noted that your system performs best when everything is synchronous, ie:  if your cpu bus speed is 266MHz, that means your system bus is 133MHz and your memory should be set to perform at 266MHz.  Setting the memory higher than the FSB of the cpu can often result in slower performance, believe it or not.

If you have a 400MHz cpu FSB, then you get your best performance using 400MHz DDR memory and ensuring both are clocked accordingly in your system setup.

DDR stands for Double-Data-Rate and is a kind of SDRAM (Syncronous Dynamic Random Access Memory).  Dual-Channel refers to being able to run two sticks of RAM in individual channels instead of one, increasing overall memory throughput, thus increasing performance.  Dual Channel DDR memory is slightly faster than Single Channel DDR memory because of it's design, but you need a motherboard capable of doing it and two IDENTICAL sticks of memory for it to operate properly.