By Katie Marsal

Published: 09:00 AM EST (06:00 AM PST)

Performance and the Upgrade Question

Our first temptation in reviewing a new Mac is to compare its performance against the previous generation. But in terms of absolute performance, the new 2.4GHz, 24-inch model is only modestly faster than its 2.33GHz predecessor and gains mostly from the added bandwidth from the 800MHz system bus as well as the expanded 4GB memory cap, up from 3GB. Compared to the outgoing model, the new version is a much better value for money: at $1799, the new system is easier to rationalize than the model it replaces, which could only reach 2.33GHz through a build-to-order upgrade. A 2.8GHz version of the new iMac is also available, but whether its clock speed, 2GB of RAM, and larger 500GB hard drive are worth the $500 premium is outside the scope of this review.

Other changes are helpful but often feel as though they fall short of what could have been. The Radeon HD 2600 Pro is a long, long overdue replacement for the GeForce 7300 GT in the last 24-inch model and an even longer-awaited replacement for the Radeon X1600 in 20-inch models. Informal 3D gaming tests have the iMac providing very playable frame rates in Quake 4 at 1024x768 resolution with all details on; while this may disappoint gamers looking to switch from a Windows PC, it's a definite improvement and should be good enough for semi-serious gameplay. We nonetheless wish Apple had taken absolute performance into account. NVIDIA's GeForce 8600 GT isn't significantly more expensive, but it's known to be significantly faster in most tasks.



Apple's continued insistence on installing 1GB of RAM in a top-end iMac is also baffling. At its price, most equivalent Windows PCs today will easily sell with 2GB or more, even with a 24-inch display in tow. Upgrading that memory is at least easier than for the previous model; the new iMac puts all 1GB in a single slot and frees up the second slot for a quicker and less expensive upgrade.

What may define the new iMac the most is its relation to far older systems than the late 2006 refresh, however. For existing Mac users who follow the typical two- to three-year upgrade cycle -- including your reviewer -- the aluminum model represents the first real opportunity to jump to Intel processors and a test of just how far Mac performance has advanced since the last PowerPC iMacs were on store shelves.

In our benchmark tests against the last 20-inch iMac G5, the new 24-inch Core 2 Duo is simply in a different class of performance. Most tests which focus on the CPU show that just one of the two 2.4GHz Intel cores can nearly double the speed of the 2.1GHz PowerPC chip; in tests aware of multiple cores, the newest Core 2 Duo is well over three times faster. Cinebench was especially impressive and saw 3D models render in just a third of the time. Quite simply, there's no more reason to cling to a PowerPC system except for very old or very specialized software that refuses to run in Apple's Rosetta environment.







On Page 3: Conclusions and Reservations, and Rating.