Overclocking on the ASUS P5K3 motherboard proved to be interesting. To start overclocking I kept the FSB the same and tried to see just how tight I could get the timings to see what I could get. At the stock voltage of 1.9V, the system was able to post with a command rate of 1T, but with a voltage increase on the memory 1T was easily reached.
To start things off I left the voltages and timings alone to see just how far I could get with 1.90 Volts on the memory. With the default timings of 7-6-6-24 and an agressive 1T Command Rate I was able to reach 1764MHz, which is an extra 164MHz over the stock clock frequency of 1600MHz. When I tried to lower the RAS to CAS Delay to 5 or the CAS Latency to 6 the system would post, but would blue screen on the Windows XP splash screen. Happy with this stable overclock that was proven by running Memtest, double Super Pi runs and RST Pro testing I then increased the voltage.
Now that we know how tight we can get the timings and how far they can go on stock voltages the next step it to increase the voltage and find the new max of the memory kit. OCZ EVP (Extended Voltage Protection) is a feature that allows performance enthusiasts to use a VDIMM of 1.95V without invalidating their OCZ Lifetime Warranty, so I increased the voltage from 1.90V to 1.95V. With just a 0.05V boost on the memory I was able to get the kit up to 1840MHz with 7-6-6 timings. The BIOS was still set for a Command Rate of 1T, but in CPU-Z it was showing up at 2T for some reason. Keeping the voltages within warranty range this kit was able to go from 1600MHz to 1840MHz with 7-6-6-24 timings, which is impressive.
Instead of using 7-6-6-24 timings I wanted to see what happened with 8-8-8-24 timings and the results were impressive. With the Intel Core 2 Duo E6750 processor running at 509MHz Front Side Bus, I was able to reach 2036MHz at 2.25V with 8-8-8-24 2T timings. It was of couse not stable at these settings, but it was stable at 2,000MHz at 500MHz FSB with 2.20V.
The best Sisoftware Sandra XII benchmark score that I was able to pull off was just over 9,800MB/Sec, which was done at 8-8-8-24 2T timings at 2000MHz. It should also be pointed out that these modules have EPP and XMP support as seen in the CPU-Z screen shot pictured above.