Testbed and Methods
After we checked all DDR400 SDRAM memory modules currently available in the market, we found they boasted strikingly different parameters. The timings of memory modules we considered varied from 2-3-3-5 (CAS Latency – RAS# to CAS# Delay – RAS# Precharge – Active to Precharge Delay) by best specimens from OCZ Technology and Corsair to 3-5-5-10 in relatively low-cost no-name modules that had flooded the stores. That’s why we benchmarked the system with the 400MHz bus and DDR400 SDRAM, setting different timings. This will also help us determine their effect on system performance and prove the necessity of using high-quality DDR400 modules. As for DDR333 and DDR266 memory modules, most manufacturers now offer products capable of working with the lowest 2-2-2-5 timings. So, we used these timings when we tested the systems with the 333MHz and 266MHz memory bus. Thus, we will be able to see whether slower DDR400 memory can outperform the faster DDR333 in practice and also whether it’s reasonable to use DDR400 plus the 400MHz bus instead of DDR333 plus the 333MHz bus.
The system we used for our test session was based on NVIDIA nForce2 chipset. This chipset is most popular today among enthusiastic users thanks to its high performance, dual-channel architecture and advanced networking and sound capabilities. As this chipset works best in the synchronous mode, all the tests were run at identical system and memory bus frequencies.
But when we were thinking of a mainboard for our experiments, we faced a certain problem. It turned out that many nForce2-based mainboards don’t allow raising the FSB frequency synchronously with the memory frequency over 180-190MHz. This is a disappointing fact, which may become a serious obstacle for Athlon XP processors supporting 400MHz bus. Anyway, we did find a mainboard, free from this problem. This was ABIT NF7. Unlike mainboards from other makers, ASUS, Chaintech and EPoX among them, this mainboard allowed increasing the FSB frequency synchronously with the memory frequency up to 225MHz, at least.
ABIT NF7 owes this amazing feature to a well-thought design as well as to the ability to send increased voltage to the North Bridge of the chipset. So, the stability of the chipset grows up considerably. However, other mainboard makers are working on this problem and promise to roll out new revisions of their products that would work in the synchronous mode at 200MHz FSB or higher.
To check the dependence of Athlon XP CPU performance on the system bus frequency, we took a CPU working at exactly 2GHz. This 2GHz clock-rate was set as 10x200MHz, 12x166MHz or 15x133MHz.
Now, let’s welcome our testbed:
- AMD Athlon XP (Thoroughbred) CPU 2GHz;
- ABIT NF7 mainboard (NVIDIA nForce2 chipset, BIOS version 15);
- 512MB DDR SDRAM (2x256MB);
- ATI RADEON 9700 PRO graphics card (Catalyst 3.1 driver);
- Seagate Barracuda ATA IV 80GB HDD.
As said above, we used different memory modules; their timings are specified in test results. All the memory was used in dual-channel mode. The benchmarks ran in Microsoft Windows XP Professional SP1 OS. The BIOS of the mainboard was set to maximum performance.