AMD CPU head to head - AM2 vs S939! - AM2vsS939 H2H - Memory explanation
Author: Grga Curkovic
Date: 23 May 2006

Now that we know the basics of memory operation we can fully understand what DDR2 advantages are. Since the time needed for the capacitor to charge and discharge is limited by some physical effects DDR2 relaxed the latencies and increased frequencies. The relaxed latencies however did not reduce latency measured in seconds since the frequency went up. So as you have already probably concluded, DDR2 modules didn?t improve latencies but gave us extra memory bandwidth. Most of the DDR2-800 modules available today work at CL4-4-4-12 while the best DDR-400 modules were capable of CL2-2-2-5. So in absolute time, the latencies are unchanged, but we doubled the bandwidth (in theory). The real question is what benefits from that extra bandwidth brings. The answer to this question is not that simple, different tasks use memory in a different way so some will benefit more while some may not benefit at all. But you shouldn?t worry too much about this since DDR2 is a logical evolution.
We had an opportunity to test two AM2 CPUs, a 3800+ single core and a 4600+ dual core. They both work at 2.4GHz and have 512KB of L2 cache per core. They are equal in frequency and cache to their equally named socket 939 brothers. So it seemed logical to compare them to the same CPUs at socket 939. Unfortunately we weren?t able to get our hands on a socket 939 version of 4600+ so we were only able to do a head-to-head comparison of the two 3800+ single cores. However we will post the results of an AM2 4600+ system and will update this article with socket 939 4600+ system results as soon as possible.