AnandTech: First Look: AM2 DDR2 vs. 939 DDR Performance

AM2 Memory Performance

The move by AMD from the current Socket 939 to Socket AM2 is pretty straightforward. We know the new AM2 processors will continue to be built using the same 90nm manufacturing process currently used for Athlon 64 processors; AMD does not show roadmaps with AM2 processors built on 65nm until early 2007. To this point AMD has also reiterated that AM2 will not bring any changes to the Athlon 64 core. In other words, the socket will change to the new AM2 Socket 940, but under the hood the current 939 and the upcoming AM2 940 will beat with the same heart. The only substantive difference expected with AM2 is the move from DDR memory to official AMD DDR2 Memory support.

With that in mind it is time to delve more deeply into the what is really new in AM2 - support for DDR2 memory with AMD's unique on-processor memory controller. Many have expressed expectations of remarkable performance increases for DDR2 on AM2. This would be at odds with what we have seen from DDR2 in the past. With the move of Intel's NetBurst architecture to DDR2 there were really no gains at all in memory performance. Those expecting big gains point out that the AM2 on-chip memory controller, like the Athlon 64 on-chip DDR controller, should provide much lower latency and higher efficiency than Intel's chipset-based memory controller for DDR2.

This is our first opportunity to look more closely at an AM2 DDR2 controller that might answer these questions about memory performance, since it is the first AM2 design to outperform Socket 939. Earlier AM2 spins could not match 939 memory performance, but they continued to improve. This is remarkable when you consider that new Intel processors pretty much have performed like final shipping processors some 5 months ahead of launch. AMD, on the other hand, has done most of their development work on the DDR2 memory controller in the last 3 months with just 6 weeks remaining before launch.

The most recent AM2 roadmap is still showing AM2 launching June 6, 2006 at Computex in Taipei. With just 6 weeks to go before launch, there is not a lot of time for surprises with AM2. As pointed out in AMD Socket-AM2 Performance Preview, there is not much wiggle room when OEMs expect mid-May shipments of AM2. All of this leads us to believe that our fourth spin of AM2 this year is very close to what will actually be shipping on June 6th. We can always hope for surprises, but given what AMD has said so far we should be very close to final silicon.

You already know that the AM2 does modestly outperform Athlon64 Socket 939. What will be explored here is how the memory controllers compare in latency and bandwidth, memory performance at various DDR2 settings compared to fast DDR400 2-2-2 memory, and basic overclocking performance of AM2 compared to Socket 939 when the CPU and memory are both pushed to improve performance.