SiS 648 - Taking Advantage of the P4 Situation

DDR400: Not Ready for Prime Time

The race to provide support for DDR400 is entirely marketing driven at this point, as many things are in this industry. Support from chipsets has been in place for quite some time; the SiS 648 unofficially supports the frequency, the P4X400 does and NVIDIA’s upcoming nForce2 does as well.

With the Pentium 4, DDR400 has the potential to offer a reasonable performance gain over DDR333 courtesy of the platform’s high-bandwidth FSB. However, the DDR400 modules that are currently available (not publicly) are of very low yield and don’t offer any real performance benefits over DDR333. This will change as yields improve and chipset manufacturers can tune their memory controllers for DDR400 operation, but that won’t realistically happen until well into 2003. The main limitation for DDR400 adoption at this point will be module availability and chip yield.

We ran through our tests with both DDR333 and DDR400 modules where possible, using a 256MB Twinmos module with CAS 2.5 Winbond chips for the DDR400 tests. There were only two platforms in this comparison that would work with DDR400: the SiS 648 and VIA’s P4X400. VIA’s P4X400 board did not run DDR400 as seamlessly as the SiS 648 reference board and was not able to produce scores in some tests; in other situations it merely crashed randomly.