This way, K8 CPUs based on E core revision allow using DDR400 SDRAM in the dual-channel mode in the following cases only:

At first glance there is nothing really bad about increasing the timing setting in case of four double-sided memory modules. However, in some cases this can cause certain issues.

First, four double-sided memory modules can appear in the system after your next upgrade. A pair of 512MB modules, which are mostly double-sided, is the most frequent configuration today. Over 40% of systems used by computer enthusiasts today are equipped with two 512MB modules. The most natural way of increasing the capacity of your system RAM in this case is by adding another pair of 512MB memory DIMMs, which will result into the total memory capacity of 2GB. However, it is far not a simple question if the performance increases as well in this case, because you will have to raise the Command Rate timing to 2T.

I have to stress that switching to 1GB memory modules will not be a panacea in this case. The thing is that 1GB memory modules are still quite rare and expensive. Moreover, they cannot boast very aggressive timings because of their high capacity.

As a result, it looks like every owner of an Athlon 64 based system can one day get four memory DIMMs installed. In order to better understand what this sort of upgrade can actually mean for the overall system performance, we decided to run a few benchmarks on our Athlon 64 (Venice) based system and compare the results of a configuration with 1GB of RAM (2 double-sided 512MB modules) against those of a configuration with 2GB of RAM (4 double-sided 512MB modules).

For our tests we assembled two testbeds, which differed from one another only by the amount of system memory and the number of DIMMs installed. These systems were built with the following hardware components:

• CPU: AMD Athlon 64 3800+ (Socket 939, 2.4GHz, 512KB L2, E3 core revision aka Venice);
• Mainboard: DFI NF4 Ultra-D (Socket 939, NVIDIA nForce4 Ultra);
• Memory: Corsair CMX512-3200XLPRO, 4 x 512MB, 2-2-2-10;
• Graphics card: PowerColor RADEON X800 XT (PCI-E x16);
• Storage: Maxtor MaXLine III 250GB (SATA150);
• OS: Microsoft Windows XP SP2.

First of all let’s discuss the results of synthetic benchmarks showing the actual memory subsystem bandwidth and latency:

The size of the installed RAM doesn’t affect the results in these synthetic benchmarks at all. So, I would say that what we see is pretty natural: the system with four double-sided memory modules appears slower than the system with only two double-sided memory modules. And this is true for both: latency and bandwidth measurements.