Pentium 4 v Athlon XP: How we tested

Intel’s new Pentium 4 processors work with chipsets that support the 533MHz frontside bus. The first available chipset from Intel is the Rambus-only 850E. However, the memory clock in this chipset remains unchanged at 400MHz, which means that it only supports PC800 memory. Note also that you must use 40ns PC800-40 Rambus memory in the new 533MHz-bus systems, not 45ns PC800-45 memory. Some third-party motherboard manufacturers support the new PC1066 Rambus, which does have a 533MHz memory clock, and Intel’s D850EMD2 and D850EMV2 boards will also function with the new memory. However, be warned that this is outside the official specification and you can’t expect support if problems arise with PC1066 memory.