ocworkbench.com har travlt

ECS is gaining lots of attention these days with its ever popular ECS
K7S5A - a SiS735 based mainboard. The popularity of it generated much
interest in the SiS chipsets as it has the best price/performance ratio to
date. ECS has made it again as the first company to mass product the SiS645
based P4 DDR mainboard. The SiS645 chipset needs no introduction as it has
proven itself in most previews done at various websites. It is a one of the
strongest contender among the P4 chipsets.

To date, Intel has only introduced Brookdale (i845) which does paralysed the
P4 system performance with bundling it with SDRAM. The problem with SDRAM is
that it deters the real performance of the Pentium 4. As we can see, the
next logical step would be to go with DDR, but Intel only licensed this
technology to SiS and ALi. That is also why you don't see many manufacturers
producing P4 DDR boards using P4x266 which is still in a licensing battle.
With VIA producing their own boards now, the chipset war is between P4x266
and SiS645. The next probably chipset to watch out for is ALi ALADDiN P4.
While SiS645 supports DDR333, P4x266 only supports DDR266.

http://www.ocworkbench.com/hardware/elite/p4s5a/p4s5ap1.htm