As the industry waits for Apple to release its first Intel powered Mac, watchers wonder which Intel chip will lurk within.

Macworld US is offering a guide to what is on offer from Intel and speculates as to what Intel processor Apple might use for which Macs.

The Pentium 4 (P4) is designed for desktops and desktop replacement laptops. It's 64-but but generally does less per clock cycle than competing CPUs. Some P4 models also feature Hyper-Threading, which creates two virtual CPUs to improve performance when running simultaneous tasks.

Intel's Pentium D is used for desktops and performance laptops. It is manufactured using a 90-nanometer process. Macworld explains that D stands for Dual-core, which means there are two execution cores on the same chip. "It’s essentially the same concept as a dual-processor G5, except that the CPUs and support logic are found on a single piece of silicon," writes Jon Jacobi. Pentium D CPUs are especially adept at multi-tasking

The Pentium 4 Extreme Edition is designed for Gaming and performance desktops. It is essentially a Pentium D with Hyper-Threading enabled, meaning two physical processor cores split via Hyper-Threading for a total of four virtual CPUs.

Pentium M is used for laptops. Unlike the other chips it isn't based on the P4 core. It's available in clock speeds from 1.5- to 2.13GHz and outperforms the G4 in Apple’s fastest notebooks as well as being economical on power consumption – it last more than five hours on a single battery charge.

Finally, the Celeron is designed for budget desktops and laptops. It is low-priced but 32-bit-only. It also features a slower front-side bus and less cache.