VIA and SiS Battle for Supremacy: 3-way P4 DDR Motherboard Roundup

Looking at DDR400

With DDR400 memory, the P4X400 and SiS 648 chipsets are able to provide Intel’s Pentium 4 Northwood-B (533MHz FSB) processors a peak bandwidth of about 3.2GB/s. This is the largest available bandwidth the Pentium 4 has ever seen supported by a DDR chipset. Only Intel’s 850E chipset outfitted with dual channel PC1066 RDRAM provides greater theoretical bandwidth than the P4X400 and SiS 648 chipsets do with single channel DDR400.

However, current DDR400 memory is essentially overclocked DDR333 relabeled as DDR400. DDR333 is now a JEDEC-approved specification whereas there is no spec for DDR400, hence the reason why there only exists overclocked DDR333. Generally speaking, with a JEDEC-approved specification comes lower memory latency and better timings than just overclocking a previous technology and relabeling it. Even though DDR333 has considerably less available theoretical bandwidth compared to DDR400, DDR333 is in fact competitive with DDR400 if you purchase the right kind. For example, CAS 2 DDR333 from Samsung will perform more or less equal to the best DDR400 currently available on the market (whose CAS Latency is still no better than 2.5).

We tested with Twinmos DDR400

If you remember, DDR333 was once in the same situation as DDR400 is in today. Back then, DDR333 was nothing more than just DDR266 overclocked to DDR333 speeds. Weeks later, real DDR333 started hitting the streets and with that finally came some noticeable performance gains over DDR266. If the DDR333 situation of several months ago has taught us anything, it’s to wait for the real thing. Therefore, we suggest that everyone wait for real DDR400 to hit the market.

Looking ahead, if JEDEC ever does finally approve a spec for DDR400 memory, that will likely be the last frequency we see out of DDR-I technology. DDR-I is clearly reaching its physical limits, and a new design needs to be implemented to reliably scale past DDR400 speeds. As you might already know, DDR-II is this new, more scalable design. The current timetable for DDR-II’s initial availability is mid-2003, but because this timetable is only for first shipments, DDR-II probably won’t have a significant impact until months later. However, we have reason to believe that as early this winter we will see DDR-II products in the form of high-end graphics cards. NVIDIA’s next generation NV30 GPU is rumored to include DDR-II technology, and we’re sure ATI won’t be snoozing at the wheel in implementing DDR-II for their recently introduced R300 architecture.