FAQ: Which Intel chip is right for your new iMac?

Computerworld - Since Apple Inc. recently refreshed its iMac line with chips from Intel Corp.'s Core i Series, some users might be left wondering which processor would work best for them.

Apple announced in late July that it is adopting Intel's Core i3, i5 and i7 chips for its iMac line of desktop computers. The move meant Apple was casting aside Intel's older Core 2 series of chips for the newer versions.

This means that for the first time, iMacs are moving on from the Core microarchitecture to the Nehalem architecture on which the Core i Series is based. But for a user who wants to get work done, play online games or upload video to YouTube, what difference does the chip make? And what do users need to take into consideration when forking over the cash to buy an iMac, or any desktop or laptop, running an i3, i5 or i7 processor?

There is quite a bit to consider.

Overview

OK, so what is it we're looking at here with the Core i Series? The series includes dual-core, quad-core and even six-core chips for desktops and laptops.

What may be a bit surprising to those who don't follow processor progressions closely is that Intel has moved its dual-core and six-core chips to a 32-nanometer manufacturing process, but its quad cores are still on a 45nm process.

The 32nm Core i Series chips, code-named Westmere, are still based on the Nehalem architecture but are built on a smaller platform. The 32nm chips have more transistors than their predecessors, have built-in graphics and will run faster without consuming more power.

None of the quad-core chips in the Core i Series, whether they're the i5 or the meatier i7 processors, have been moved from the 45nm process to the 32nm process. And George Alfs, an Intel spokesman, said the quads won't be moved to a Westmere version. Instead, they'll transition to Intel's upcoming "Sandy Bridge" family.

Sandy Bridge, which is scheduled to go into production in the fourth quarter of this year, is Intel's next chip architecture. When the quad-core chips move to a 32nm process, it will be part of that move.

Industry analysts say they expect to see desktop and mobile systems with the Sandy Bridge chips hit the market early in 2011.

A closer look at the chips

Core i3

Core i3 chips make up the low end of the processor line for the Core i Series. They are all dual-core chips (so they're all 32nm) for desktops and laptops. Most have hyperthreading but none have turbo boost. The i3 chips have the same processor as the i5 dual cores, but they lack some of the i5's bells and whistles.