Hooray. Apple hasn't forgotten about the Mac Pro. In the 16 months since Apple last updated its Mac powerhouse the iMac had gained Core-i5 chips and in many of our tests performed better than the Mac Pro's Xeon processor. All that seems set to change: the Mac Pro has been given a boost with Intel's new Xeon Westmere technology, and as a build-to-order option you can boast that your Mac has, not four, not eight, but 12 cores!

But why would you need all those cores? Here's some history to set the scene. In June 2003 Apple's Steve Jobs promised that within a year Apple would introduce a 3GHz Power Mac G5, but the 3GHz version never materialised, and in August 2006 the IBM-powered Power Mac was replaced by the Intel-powered Mac Pro. Even so, it took time before 3GHz chips appeared as options in Macs. Right now the only +3GHz Mac Pro is built-to-order (although, thanks Turbo Boost, you can get dynamic performance of 3.06GHz from a 2.8GHz chip). Instead of GHz-galore we have dual-cores, quad-cores, 8-cores, and 12-cores to contend with. Why?

Back in the 90s computing power was measured by how many megahertz or gigahertz your machine offered. Apple was busy telling everyone this was not how to compare computers, coning the phrase 'Megahertz Myth'. To prove the point, in 1997 Apple claimed its G3 outperformed the Pentium II while consuming less power, while Intel promoted the higher clock rate of the Pentium II.

It's how much power is consumed that is key here. The laws of physics decree that increases in clock rate equal increases in heat. As a result there are very few commercial PCs that boast more than 4GHz.

The trick is to find a way to improve efficiency without consuming more power and creating more heat. So rather than make the CPU faster, add more processors (or cores) to the chip and double your computational power.

That all sounds great, but software has to be written to take advantage of multiple cores. It's no good getting extra cores if your software doesn't support them. So before you spend a fortune on a 12-core Mac make sure you have the software to take advantage of this ultimate Power Mac.