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New build-to-order iMacs impress with speed

13.05.2011
When Apple released new in early May, the company also made available new build-to-order (BTO) options in addition to the . Macworld Lab tested two iMacs with BTO processor upgrades that offer faster speeds and more processing power, and the results show that the additional cost for the upgrades are worth it--if you run software that takes advantage of the technology.

Processor upgrades are optional for two of the four standard-configuration iMac models. For the $1499 model, an upgrade to a 2.8GHz Core i7 quad-core processor is available. For the $1999 , you can upgrade to a 3.4GHz Core i7 quad-core processor. Each upgrade adds $200 to the price of the respective standard-configuration computer.

The standard-configuration iMacs use processors that do not use Intel's technology, but the Core i7 upgrades do support the technology. Hyper-Threading allows two processing threads to run on a single core. In the case of a quad-core processor, Hyper-Threading would present the operating system with eight virtual cores. This can allow for faster processing. The only way to get Hyper-Threading on the new iMacs is to buy the BTO Core i7 processor option.

However, many applications do not make efficient use of multiple cores, so going from four cores to eight virtual ones doesn't make a lick of difference. Some applications, however, can and do make use of all of those cores. Processor-intensive applications such as HandBrake, Cinema 4D, and Mathematica benefit greatly from Hyper-Threading.

Whether the upgrades are worth the additional cost depends on what you plan to do with your iMac. Our system performance test suite, , produced results that show that the 21.5-inch iMac with a BTO 2.8GHz Core i7 processor is about 7 percent faster than the standard 21.5-inch 2.7GHz Core i5 iMac. The 27-inch iMac with a BTO 3.4GHz Core i7 processor is about 11 percent faster than the standard 27-inch 3.1GHz Core i5 iMac.

In individual tasks, the 21.5-inch 2.8GHz Core i7 iMac was more than 15 percent faster than the standard 21.5-inch 2.7GHz Core i5 iMac when importing a camera archive into iMovie, 18 percent faster in our HandBrake encoding test, 22 percent faster in MathematicaMark, and 25 percent faster in the Cinebench CPU test. The BTO 21.5-inch iMac was 11 percent faster overall than the $1199 21.5-inch 2.5GHz Core i5 iMac, and 21 percent faster in our iMovie import test, 24 percent faster in HandBrake, 30 percent faster in Cinebench's CPU test, and 31 percent faster in MathematicaMark.