Intel yesterday formally began selling its Pentium 4 6xx series, rolling out four versions of the 90nm, 2MB L2 cache chip. The chip giant also added its latest P4 Extreme Edition to its official price list. The P4 630 (I got one of these), 640, 650 and 660 are clocked at 3, 3.2, 3.4 and 3.6GHz, respectively. All four chips support an 800MHz frontside bus. They also bring Intel’s AMD64-like 64-bit addressing technology, EM64T, to the mainstream desktop, along with the latest version of the company’s SpeedStep power management system, to minimise energy consumption. The anti-virus ‘execute disable’ bit is also supported.