In two weeks, Intel will increase the clock speed of its Pentium 4 processor for possibly the last time as the company heads into a new era for its desktop processor designs.

The Pentium 4 570 processor is a 3.8GHz chip with 1MB of Level 2 cache that will feature the fastest clock speed of any Pentium 4 processor for an indefinite period of time. It will lead Intel's mainstream desktop segment when it is released on November 15, Intel confirmed.

Intel's shift away from clock-speed frequency as a central design philosophy has been well documented this year. In May, the company cancelled plans for two high-frequency single-core processors in favour of an acceleration of dual-core designs due by the end of 2005.

More recently, plans to release a 4GHz Pentium 4 were scrapped last month after Intel decided the effort required to reach that milestone would not be worth the expense.

Increasing the Pentium 4's clock speed has been a mantra at Intel almost since the chip was released in 2000. But starting in the first quarter of 2005, Intel will improve the performance of the Pentium 4 processor by adding cache memory.

Several processors running at 3.8GHz and slower will receive the extra memory, which improves performance by permitting the chip to store larger amounts of frequently accessed data close to the processor.

After that, dual-core chips are expected in the second half of 2005 that will run slower than existing Pentium 4 processors. Chips running at 4GHz or faster might eventually surface for low-cost PCs, said Nathan Brookwood, principal analyst with Insight 64 in California.

Intel currently builds low-end chips like the Celeron processor by disabling half of the Pentium 4's cache memory. But disabling an entire processing core on a dual-core chip would probably be considered a waste of silicon, Brookwood said.

The company could keep a single-core processor design for low-end PCs could be manufactured in smaller sizes than dual-core desktop chips and help reduce Intel's manufacturing costs for that product line, Brookwood said.

The improvements in power consumption that are expected along with the arrival of the 65 nanometre process generation around the end of 2005 will also help make a 4GHz clock speed a reality for budget chips based on a single-core design, he said.

Intel is expected to release two versions of a dual-core desktop processor based on the current Pentium 4's Netburst architecture in late 2005 or early 2006. But starting in 2006, Intel is expected to begin a shift toward using the Pentium M in desktop PCs. The Pentium M delivers comparable performance to the Pentium 4 on most applications while running much slower, and therefore using much less power.

This will be true even when the dual-core Pentium M, code-named Yonah, launches in 2005. Even if Intel made no changes to the current Pentium M design to improve power consumption on Yonah, which is unlikely, a dual-core Pentium M running at around 2GHz would consume about 40 watts of power. This is far less than the 115 watts consumed by the fastest versions of the Pentium 4.