FSB Overclocking: Synchronous Only, Please!
We tested DDR466 memory on a standard nForce2 system and saw poor results. The higher clock speeds failed to produce much in the way of performance gains. First, the memory modules did not support super-fast timings. Second, the memory operated asynchronously to the FSB clock speed.
Anyone who regularly uses different chipsets will soon realize that the models from the house of Intel do not generally allow asynchronous memory operation. The reason lies in the only slight advantages offered by this mode : The overhead or wait times are simply so large that the theoretically higher data rates cannot be translated into performance gains.
But, as impressively supported by our benchmarks, simultaneously raising both FSB and memory clock speed makes the most sense by far.
Memory Timings Irrelevant ?
What is striking about our results is that all available fast memory modules for 466 MHz and up do not support CAS latency of 2.0 clock cycles. Not too long ago, this CAS latency support was considered second to none in the quest for maximum performance. This appears to have considerably less impact on Intel’s latest chipsets in the 865 and 875 range than was the case with earlier models, such as the 845, and with Athlon chipsets from nVIDIA and VIA.
We conducted a variety of tests in which we operated DDR400 memory at ideal timings (2-2-6, CL2.0) before repeating the readings at conservative timings (3-3-6, CL2.5). While the variance is measurable, they were voided if the system-clock speed was raised only slightly. A mere 3 MHz of extra FSB speed is enough to outperform the optimized system with run-of-the-mill timings, which clearly demonstrates how much the Pentium 4 profits from high-system clock speeds. However, it also shows that pursuing ideal timings on the Pentium 4 is a waste of time.
Corsair TWINX PC4000
PC3700 Or PC4000 : The Shape Of Corsair’s DIMMs
Corsair was the first company to offer tested and packaged pairs of DIMMs. Called TWINX, they are available in the usual capacities and in several quality grades. PC4000 is specifically designed for overclocked Pentium 4 systems and thus does not support fast CAS latency times of 2.0 clock cycles. However, if the automatic memory recognition (by SPD) is not activated in the BIOS, the TWINX-DIMMs run at a mere 3-4-4-8. If they’re run separately, 2.5-4-3-6 is possible, but that hardly makes sense with dual-channel platforms available today.
