Lab tested: 21.5-inch Core i3 iMac/3.06GHz benchmarks

On Monday, Apple updated its entire line of iMac and Mac Pro systems. And while the new Mac Pro models won’t be available until sometime in August, the new iMacs are in the Macworld Lab right now.

The first system to finish our testing regime is the new entry-level iMac, a 21.5-inch model with a 3.06GHz Core i3 processor, and our Speedmark 6 test results show an impressive performance improvement over the system it replaces.

In the last generation of iMac, all but the highest-end standard configuration continued to use the older Core 2 Duo line of processors. But these new iMacs have now completely transitioned from using the Intel Core 2 Duo processors to Intel Core i3 and Core i5 processors. The Core i3 processor used in this iMac supports Intel’s Hyper-Threading technology, which gives the two-core processor four “virtual cores” for better performance in multithreaded applications.

Another positive step is the inclusion of discrete graphics across the entire product line, with the entry-level model using the ATI Radeon HD 4670 graphics previously available on just the two middle-tier systems of last generation. (The Nvidia integrated-graphics technology used in the previous generation of iMacs isn’t compatible with the Core i3 processor, so a change was inevitable.)

In addition to the 3.06GHz Core i3 processor and Radeon HD 4670 graphics with 256MB of dedicated GDDR3 SDRAM, the new entry-level iMac includes 4GB of 1,333MHz DDR3 SDRAM and a 500GB hard drive for $1199—the same price as the model it replaces. That older model had Nvidia GeForce 9400M integrated graphics, a 3.06GHz Core 2 Duo processor, the same 500GB hard drive, and 4GB of slower 1066MHz DDR3 SDRAM.

In our tests of the new entry-level iMac, we found that the new system was a little more than 20 percent faster overall than the Core 2 Duo system it replaces, and just about 9 percent faster than the previous $1499 3.2GHz Core 2 Duo model. We saw impressive improvement over the previous 21.5-inch systems in processor-intensive tasks, like MathematicaMark (40 percent), Cinebench (25 percent), and Compressor (11 percent).

The biggest gain, however, was in graphics performance. The previous entry-level iMac, with its integrated graphics, lagged well behind the new Core i3 iMac with the Radeon HD 4670 discrete graphics. The new system was able to display nearly four times as many frames per second as its predecessor. It even bested the old $1499 model by 12 frames per second.

But faster though the new Core i3 system is, it’s still 15 percent slower than the previous top-of-the-line quad-core 2.66GHz Core i5 iMac. That quad-core i5 system was 29 percent faster in Cinebench, 60 percent faster in MathematicaMark, and about 20 percent faster in Compressor. Interestingly, the new 3.06Ghz Core i3 was faster than the quad-core 2.66GHz iMac in iTunes import and WorldBench multitasking tests.

We’re busy testing the rest of the iMacs, so check back soon for more test results and full reviews of the new systems.