You're either trolling or clueless. Rambus is better than SDRAM, but the ancient 850 is no match for current dual channel DDR setups. And wanting to plug a $1000 cpu in a 533 MHz board really makes me wonder what you sell your customers...
If you love rambus so much (even more than intel, which has abandonded it for good reason), you can always get a SiS R659 based motherboard; at least it supports 800 MHz FSB P4's and up to PC1200 RDRAM if you can find any. With PC1066 it might perform only a little worse than a typical 875 setup with DDR400 costing roughly 3x less instead of MUCH worse with a 850 with 533 FSB and PC800.
Sounds like a good deal for you, in combination with a P4EE you'll have a super expensive setup that gets trashed by A64/FX systems and probably even 875/P4C systems costing only a fraction; but hey, its super expensive and rare, so therefore it must be good, right ? Have you considered buying a $4.000 Itanium 2 with 6 MB cache ? those things run windows and x86 software as well, and are expensive as hell. I bet they are even better !
Enjoy !
= The views stated herein are my personal views, and not necessarily the views of my wife. =