AMD has led the 64-bit desktop processor field up to now with the Athlon 64 -- although there is, as yet, no shipping 64-bit Windows operating system, which is necessary to make the most of a 64-bit CPU. However, at the beginning of February Microsoft made Release Candidate 2 of Windows XP Professional x64 Edition available to testers, and the final version is due to ship at the beginning of April.
With its 6xx-series Pentium 4 processors, Intel has finally jumped on the desktop 64-bit bandwagon. Intel's EM64T architecture can implement Windows' x86-64 mode, and is also compatible with the AMD64 architecture. This means that you don't need different Windows operating systems to take advantage of 64-bit processing.
Intel's new processors offer some other innovations besides the 64-bit EM64T architecture. For example, all 6xx-series CPUs deliver 2MB of Level 2 cache -- double the amount on the 5xx-series chips. There's also improved power management in the shape of Enhanced Intel Speedstep Technology (EIST) and protection from malware infection via memory overflow thanks to the eXecute Disable (XD) bit.
The 6xx-series Pentium 4 chips have an 800MHz frontside bus (FSB) and are designed for use in standard desktop PCs. Intel is also offering a new Pentium 4 Extreme Edition clocked at 3.73GHz with a 1,066MHz FSB. This expensive ($999), high-end chip is only likely to appeal to a limited market -- mainly power users and gamers.
According to Intel, the 6xx-series Pentium 4s will replace the older line in the medium term. However, it may be some months before you can no longer buy 5xx-series chips.
|6xx-series Pentium 4 processors|
||Level 2 cache
||EM64T / XD / EIST
|Pentium 4 660||3.6GHz||2MB||yes / yes / yes||$605|
|Pentium 4 650||3.4GHz||2MB||yes / yes / yes||$401|
|Pentium 4 640||3.2GHz||2MB||yes / yes / yes||$273|
|Pentium 4 630||3.0GHz||2MB||yes / yes / yes||$224|