Review Once you've invested a few billion dollars in a fabrication plant and have a team of skilled engineers beavering away, you'll find it relatively easy to design and build an x86 processor. As time goes by you have to develop it to reduce production costs, raise efficiency and to increase its speed. Over the last 20 years we've seen chip manufacturers go through a ritualised dance to keep moving things along. Every few months they raise the clock speed multiplier. If things get tough, the engineers can increase the size of the L2 cache, writes Leo Waldock.
The real bonanza comes when the fabrication plant is ready to move to a new production process. The move from 250nm (Pentium II and III 'Katamai') to 180nm (Pentium III 'Coppermine' and Pentium 4 'Willamette') and on to 130nm (Pentium 4 'Northwood') has reaped huge returns. As the process reduces in size, Intel has been able to fit more transistors into the same area, or make the core smaller and cheaper. It's been able to continue upping clock speeds.
In short a new fabrication process is a joyous experience which offers the potential of massive profits - if it works.
As the processes have shrunk, chips have been experiencing some unusual physical effects. The main problem is quantum tunnelling. At school we're taught that atoms are like planets with electrons orbiting around them like moons. It's a neat image but quite inaccurate. According to quantum theory, atoms and electrons don't inhabit a fixed space but instead exist in a number of locations at once until they are fixed by being observed. It sounds like a plot line from Star Trek but it's an unfortunate fact of life that electrons leak through materials that appear to be solid. This errant behaviour has never been much of a problem before, but the big crunch came when Intel moved to the 90nm 'Prescott' Pentium 4.
Instead of seeing the usual gains of reduced power and raised speeds, Prescott actually worked slower than the previous Pentium 4. Intel had increased the length of the pipeline inside Prescott to make it easier to raise clock speeds in the future. That should have been invisible to outside observers, but we all noticed the performance hit, and none of us could ignore the TDP (Thermal Design Power) which broke past the 100W mark.
Intel responded swiftly by canning development of the 65nm 'Tejas' Pentium 4 and, soon after, by dropping the 4GHz Prescott. It also chose to accelerate development of dual-core processors. As far back as 1989, Intel's engineers knew that the day would come when conventional processors would grow too complicated and expensive, and the best way to increase processor performance was to add extra processing cores.