Anyway, the P4PB 400 mainboard disappointed me with its unstable operation with DDR400 memory. Moreover, with default settings P4PB 400 performed worse with DDR400 than with DDR333. And this situation is very hard to change for the better even during fine tuning. VIA comments on this as follows: "As DDR400 standard is not ratified, we increase the timings greatly to ensure stable work and it inevitably leads to lower performance". Well, quite reasonable, I should say.
The latency measurements show that VIA P4X400 with DDR400 SDRAM will not please us with good results. Memory subsystem latency is greatly increased in this case and it means that VIA didn't care about optimizing its controller for DDR400. That is, by the way, one more argument proving that VIA P4X333 and P4X400 are one and the same thing.
When encoding video into MPEG-4 format, VIA P4X400 managed to fall behind all its rivals, even those, which worked with slower memory. The only conclusion is that the VIA chipset may hardly be considered able to work with DDR400. Actually the support of this memory type is nothing but a marketing trick.
For $100, how could I go wrong 
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