FSB and DDR Clock Speed?

[mordeth]

Hey everyone,
I had a question about Front Side Bus and the different speeds of RAM. I am thinking of buying the EPoX EP-8RDA. It has a 333MHz Max FSB but it says it can handle 3 x DDR SDRAM PC3200, 3GB max. I thought the speed of the RAM was related to the Front Side Bus (I apologize for showing my ignorance ). If I coupled the AMD 2800+ with this motherboard, would say 2 x 512MB of PC3200 be worth it or should I stick with 2 x 512MB PC2700.

 

[Lord Evermore]

With chipsets for AMD processors, and chipsets from SiS and VIA for the P4, the FSB and memory bus can run at different speeds. Intel is the only one that makes the chipset limit the memory speeds based on the frontside bus speed, which is unfortunate since the P4 is the one that needs extra memory bandwidth the most.

The Athlon gets best performance when the FSB and DDR memory are running at the same speeds, because then the bandwidth is matched and there are no latency penalties. If you run them at different speeds, one bus or the other will often have to wait for part of a cycle till the other bus "lines up"; using PC3200 gives extra bandwidth that the CPU doesn't need, while having the latency issues occur. The only time that the extra memory bandwidth would be a good thing is if you have onboard video, since the video processor would need to use main memory bandwidth for texturing (or if you had an AGP card that couldn't hold everything in its own memory and needed to use AGP texturing a LOT).

 

[Batman5177]

PC2700 would be the MINIMUM to make the 2800+ run.

anything higher is only for overclocking purposes or future-proofing.

 

[mordeth]

Thanks for your replies, since I don't see myself ever overclocking, I think I'll stick with the PC2700... Thanks again guys.