DDR2 is currently supported by Intel’s 915/925 and 945/955 chipset families and nVidia’s nForce 4 Intel Edition chipset. With a system bus capable of running at 4 x 266 MHz = 1066 MHz and a maximum bandwidth of 8.2 GB/sec between the CPU and the memory controller, the just released Intel 955X chipset is the right product to test high-yielding DDR2. Our testbed is based on the ASUS P5WD2, by many regarded as the best performing 955X motherboard.
Our test system:
Processor: Pentium 4 3.73 GHz Extreme Edition
CPU cooling: air-cooled with XP-120 and water-cooled with Thermaltake Bigwater
Motherboard: ASUS P5WD2 Premium with BIOS 1008 (Intel 955X chipset)
Hard Disk: 1 SATA Western Digital WD76GB
Video Card: nVidia 6600 GT with driver 71.89
OS: Windows XP Pro, SP 2, DirectX 9c
Additionally we have tested OCZ PC2-6400 Platinum for compatibility with several 925 and 945 chipset based boards from Intel and ASUS and did not find any issue with them.
For measuring bandwidth and application performance we used:
SiSoft Sandra 2005 (Memory bandwidth)
Super Pi (Mathematical calculation to measure system performance)
PCMark 2004 Pro (Scripted applications to measure system performance)
3DMark 2001 (Synthetic gaming benchmark)
Comanche 4 (Game benchmark)
Unreal Tournament 2003 (Game benchmark)
We are intentionally using here older gaming benchmarks, because they are more focused on system performance than newer gaming benchmarks that are predominantly driven by video card performance. For this same purpose, we ran Comanche 4 and Unreal Tournament 2003 at the low resolution of 600 x 800. This takes video card performance as much as possible out of the equation. All other benchmarks were run at their default settings.
CPU-Z 1.29 does properly recognize OCZ PC2-6400 as such including SPD (default) timings. It shows also correctly the memory timings as they are set in the motherboards BIOS. But unfortunately the FSB to memory ratio is as well as the memory frequencies are wrongly reported. Although the latest version available when this article was written, CPU-Z 1.29 does obviously not yet support the brand-new Intel 955X chipset. The reader may keep this in mind when studying the CPU-Z screenshots.
The Asus P5WD2 BIOS allows setting the memory frequencies independently from the FSB frequency via 6 different FSB to DRAM ratios. By using this feature we found out that OCZ PC2-6400 does run at the frequency of 800 MHz and timings of 4-2-3 without any problem at 2.1 volt. Even 2 x 452 MHz = DDR2 904 MHz was mastered at 5-3-3 after increasing the memory voltage to 2.3 volt.
Around 910 MHz was the maximum frequency we could achieve with our test modules. When running the 3.73 GHz EE at its default FSB frequency of 266 MHz and the memory at 892 MHz the maximum unbuffered/buffered memory bandwidth we could achieve with Sandra 2005 was around 4800/6800 MB/sec. The maximum buffered bandwidth we could squeeze out, starting at FSB 266 MHz, was around 6900 MB/sec with the memory running at 2 x 452.6 MHz = DDR2 905 MHz.
Left: bandwidth at 533MHz - Right: bandwidth at 905MHz
(note that the reference graphs in the screenshots are different)