Five weeks after they were announced, the new iMac has made its way to market. Apple started shipping the 21.5 inch iMac on Friday, as well as began taking orders for the new 27-inch models.

Macworld Lab has two new iMacs, build-to-order systems with the fastest optional processors and equipped with the new Fusion Drive. While we wait for our standard configuration models to arrive, letÆs look at the performance--the very fast performance--of these maxed-out iMacs.

Inside the new BTO iMacs

The new iMacs come in four standard configurations, all with updated processors and graphics, and all with 8GB of 1600MHz DDR3 SDRAM and 1TB hard drives. The 21.5-inch models ship with either a 2.7GHz quad-core Ivy Bridge Core i5 processor and Nvidia GeForce GT640M graphics with 512MB of dedicated memory for $1299, or a 2.9GHz version of the same Core i5 CPU and Nvidia GeForce GT650M graphics with 512MB of dedicated RAM for $1499. The low-end standard configuration 27-inch iMac now comes with the same 2.9GHz Ivy Bridge quad-core Intel Core i5 processor as the high-end 21.5-inch iMac, but with Nvidia GeForce GT660M graphics with 512MB RAM for $1799. The higher-end 27-inch model uses a faster 3.3GHz quad-core Intel Core i5 processor and has an Nvidia GeForce GTX 675MX with 1GB of dedicated memory for $1999.

The BTO models we tested have Core i7 processors: a 3.1GHz quad-core version in the 21.5-inch model, and a 3.4GHz version in the 27-inch model. Both processor upgrades are available as $200 options. The 21.5-inch iMac had 16GB of RAM, a $200 upgrade, while our 27-inch model had the stock 8GB of memory. The 21.5-inch iMac had the stock Nvidia GeForce GT650M graphics with 512MB of dedicated RAM, but the 27-inch had the optional Nvidia GeForce GTX 680MX with a whopping 2GB of memory (a $150 upgrade).

Both custom iMacs include Apple's 1TB Fusion Drive. A new technology that marries a roomy 1TB hard drive to a fast 120GB of flash storage and presents them as one single drive to both the user and applications. Our previous tests show that in most instances, the Fusion Drive keeps up with the speeds of a standalone SSD, while offering the high capacity of standard hard drives. The 1TB Fusion Drive is a $250 optional upgrade to the higher-end 21.5 and both 27-inch iMacs. For those without a calculator, our BTO 2012 iMacs came to $2149 for the 21.5-inch model, and $2599 for the 27-inch model.

To see how these new custom iMacs perform when compared to previous models, as well as the Fusion Drive-equipped Mac minis we just looked at, we turned to our overall system performance benchmark suite, Speedmark 8.

In our tests, the 3.1GHz 21.5-inch iMac was 53 percent faster overall than a 2011 BTO 21.5-inch iMac with an upgraded 2.8GHz quad-core Sandy Bridge Core i7 processor, 4GB of RAM and a 1TB hard drive. The Fusion Drive in the new 21.5-inch iMac finished our file copy and uncompress tests in a third of the time of the 1TB drive in the 2011 model. MathematicaMark showed the 3.1GHz Ivy Bridge processor to be 16 percent faster than the 2.8GHz Sandy Bridge CPU found in last years model and the new system's processor helped it finish the Cinebench CPU test 21 percent faster.

We also have a 2011 21.5-inch 2.7GHz Core i5 iMac with a 256GB Fujitsu/Apple SSD, that is otherwise standard issue. The new iMac with Fusion Drive was 28 percent faster, overall. The Fujitsu/Apple SSD was comparatively pokey when compared to the Fusion Drive, taking nearly twice as long to complete our file copy and uncompress tests. The new iMac's 3.1GHz Core i7 was 21 percent faster than the older model's Sandy Bridge Core i5 in our Mathematica test and 38 percent faster in the Cinebench OpenGL tests.

Compared to the current Mac mini with a 2.6GHz Ivy Bridge quad-core Core i7 processor, 8GB of RAM and a 1TB Fusion Drive ($1249 with the upgrades), the 21.5-inch iMac was 20 percent faster overall. Many of the test resultss were similar; file copy times and uncompressing times on the two Fusion Drives were virtually identical. The biggest difference, performance-wise, was pointed out in the graphics tests with the discrete graphics of the new iMac pushing nearly twice as many frames per second in the Cinebench OpenGL test and more than twice as fast in the Portal 2 test.

The new BTO 21.5-inch iMac was also faster, about 8 percent overall, than the 15-inch Retina MacBook Pro, with its "pure" flash storage, 8GB of RAM and quad-core 2.6GHz Core i7 processor. The Retina's flash storage was a bit faster in our copy file test and in PCMark. Photoshop and iTunes was about 4 percent faster on the BTO 21.5-inch iMac. HandBrake scores showed the biggest performance differences, with the iMac finishing 38 percent faster than the Retina MacBook Pro.

The BTO 27-inch iMac was 5 percent faster overall than the BTO 21.5-inch model. Its iMovie export was 22 percent faster and Portal 2 was 15 percent faster on the new 27-inch. We compared the new BTO 27-inch iMac to a custom 27-inch from last year that had a faster 3.4GHz Core i7 processor, 2GB AMD Radeon graphics card, a 256GB SSD and 4GB of RAM. Those tests show the new iMac to be 22 percent faster overall, with better times in all but the Cinebench Open GL test, in which the AMD Radeon was faster than the Nvidia GeForce. Portal 2 scores were faster with the 6 percent faster with the new iMac and its Nvidia graphics. Again, the SSD on the 2011 BTO iMacs not as fast as the Fusion. The 27-inch iMac was 25 percent faster overall than the BTO, Fusion Drive-equipped Mac mini and was 13 percent faster than the 2012 2.6GHz Core i7 Retina MacBook Pro.

Check back soon for more results and full reviews of the new 2012 iMac family.