Benchmarks: Speedmark 8 scores
The new iMac comes with Intel's Ivy Bridge quad-core processors that share 6MB of L3 cache. The $1499 iMac has a 2.9GHz Core i5 processor, while the $1299 iMac has with a 2.7GHz Core i5 processor. The processors support Intel's Turbo Boost, which allows a processor to run faster (up to 3.6GHz on the $1499 iMac and 3.2GHz in the $1299 iMac) with processor-hungry applications.
The optional 3.1GHz Core i7 quad-core processor, a $200 upgrade to the $1499 model, offers Intel's Hyper Threading. This technology allows applications to address twice as many virtual processing cores, helpful in applications that can take advantage of multiple cores like Mathematica and Cinema4D.
The new high-end 21.5-inch 2.9GHz iMac was 12% faster than the previous high-end 21.5-inch iMac with a Sandy Bridge 2.7GHz Core i5 quad-core processor in our MathematicaMark tests and 17% faster in the Cinebench CPU test. The new entry-level 21.5-inch 2.7GHz iMac was 11% faster than the previous entry level 21.5-inch iMac with a Sandy Bridge 2.5GHz in both MathematicaMark and Cinebench CPU tests.
Apple also updated the graphics processors in the new iMacs. The ATI Radeon has been replaced by Nvidia graphics processors: the GeForce GT640M in the $1299 model, and the GeForce GT650M in the $1499 model. Our Portal 2 test results were 7 to 8 frames per second faster on the new iMacs when compared to the previous models, but the Cinebench OpenGL test results were 10 and 12% slower than the previous low and high-end iMacs, respectively.
Because of the reduced case size, Apple uses smaller 2.5-inch 5400-rpm hard drives in the new 21.5-inch iMacs, where Apple previously used 3.5-inch 7200-rpm drives. (The 27-inch iMacs still use 3.5-inch 7200-rpm hard drives.) Apple increased the cache size on these slower-spinning drives to help increase the performance. But even with the larger cache, the older iMac's 7200-rpm drives finished our file copy test faster than new iMac's 5400-rpm drives. The file unzip test was just 1% faster on the 2011 iMac.