Let me know what is going on here please.

a friend was asking me about buying some ddr2 ram for his computer with a amd x2 4200+ am2 processor. he said his computer came with ddr2 4200 speed ram and he is looking at getting ddr2 6400 and have a combined total of 2gb. I let him know that combining the ram will make the system still run at the slower 4200 speed. but if he takes the 4200 out and just puts in the 6400 speed (if his mobo and processor can handle it) then his fsb will be faster but not change his clock speed of 2.2ghz. right? if I am wrong then is his computer with 4200 speed ram actually not running up to spec?

I'm not familiar with the new am2 or dual core technology yet. so please forgive me. I've tried to find information but can only seem to come up with overall bandwidth information and none about cpu speed differences.

Shuttle AN35N-Ultra
AMD 2600B-M O/C 2.3Gig
Geil 1.5gb 3200DDR
Gforce 6800 Ultra O/C
UV Clear Acrylic Blue case

There is no FSB on the A64s because of the integrated memory controller. Furthermore, the reference clock for virtually all of AMD CPUs for a while now has been 200MHz.

X2-4200+ ⇒ 200x11 ⇒ 2200MHz/6 ⇒ PC2-6400 @ 366MHz

Note: The DDR2-800 or PC2-6400 will run at 366MHz as opposed to 400MHz because of the memory controller using a CPU/6 (whole multipliers) based memory frequency. To avoid the bandwidth hit, it is always best to stay away from those CPUs with odd multipliers.

With regards to your friend's machine, he definitely needs to use the PC2-6400 over the PC2-4200 since that is DDR2-533 @ 266MHz.

AMD systems haven't used a FSB since the introduction of the S754/A64. The memory controller is built into the CPU & the two communicate at full processor speed. In the case of the 4200+, that speed would be 2200MHz. The memory controller then communicates with the RAM at whatever bus speed the RAM is designed for...so theoretically, the faster the RAM, the better the performance.

Sabertooth made an excellent point about the multiplier.

great, I did some research and found out the basics of that beforehand , but I didn't understand why until you guys explained it. thank you.

Shuttle AN35N-Ultra
AMD 2600B-M O/C 2.3Gig
Geil 1.5gb 3200DDR
Gforce 6800 Ultra O/C
UV Clear Acrylic Blue case

I found out his mobo can support only up to 5300 ddr2. being only a 130mhz increase in speed from 4200 ddr2 would that even be noticeable?

I told him to now worry about it...save his money for a better vid card anyway..

Shuttle AN35N-Ultra
AMD 2600B-M O/C 2.3Gig
Geil 1.5gb 3200DDR
Gforce 6800 Ultra O/C
UV Clear Acrylic Blue case

DDR2 6400 would be the optimal choice considering that the AM2 Athlon 64 X2's have a (cpu memory bandwidth) ratio of 12.8GB. Thus DDR2 6400 + DDR2 6400 in Dual Channel mode = 12.8GB which will make both the cpu and ram run nysc with each other.

if DDR2 5300 is the best he can do then he needs to ditch the DDR2 4200 and buy two pair of Dual Channel DDR2 5300 which will bring him up to 10.6GB of cpu memory bandwidth. Even though 10.6GB memory bandwidth won't run nysc with his processor, it's a lot less of a bottleneck then sticking 2 DDR2 4200 sticks of ram in which only max out at 8.6GB.

It seems to me that his motherboard was more designed around a single core AM2 Athlon 64/Sempron processor then anything else, because single core AM2 Athlon 64/Sempron processors have a cpu memory bandwidth ratio of 10.6GB. Which means that Dual Channel DDR2 5300 will meet that requirment in which his motherboard supports.

AMD Athlon 64 X2 4400+ OC 2.7ghz
4GB Dual Channel DDR 3200
Nvidia 7900GT
SATA II 2x 300gig 7200rpm 16mb cache RAID-0+1
Gigabyte Nforce 4 SLI