A lot has been said for the ability to run at very high speeds whilst retaining the ability to run at tight timings with a divider. To do this we tested the Corsair XMS4400 at various speeds and latencies, all at the 2.9V we found to work best during benchmarking. At the most aggressive timings offered, CAS 2-2-2-5, the motherboard would not post. Reducing these to CAS 2-3-3-6 was 100% stable. Clearly these Hynix chips are not designed to take tRCD and tRP values of 2 at any speed. These quite aggressive timings were good up to 212MHz, after which errors started to come in. Relaxing the CAS to 2.5 bought another 7 MHz or so, but it was not until the tRCD and tRP were reduced yet further to 4 the modules begin to show their potential. 2.5-4-4-7 was good for up to around 518MHz, and at fully relaxed timings you have already seen the awesome results!
Overall then, the Corsair is more than capable at running fairly tight timings at DDR400, but it is certainly not particularly attractive in the PC3500 - PC3700 region, needing tRCD and tRP values of 4. If your chip has a sweet spot in this zone (like most 3.0GHz chips) - then aggressive PC3500 and PC3700 are much better choices.
