Previously, the lower-priced 27-inch iMac and the more expensive 21.5-inch model were built to the same specifications - only the screen size differed. This changed with a slightly better graphics card in 2012, but now the two iMacs have parted company completely, and no longer offer processor parity either. Perhaps this is why the cheaper 27-inch iMac is £100 more with this release, while the other three models only went up by £50.
As you'd therefore expect, the 3.2GHz 27-inch iMac proved incrementally faster than the 2.9GHz 21-inch model. Our Doom 3 frame rate benchmark took a modest step up to 232.6 FPS, and using all four cores, and its Cinebench score was over 6% faster. Comparing it to the similar model from as recent as the mid-2010 upgrade, it was over 123% faster in the Cinebench multi-core test, which just goes to show how much the iMacs have increased in power over the last few years.
Comparing the 3.2GHz iMac with a 3.4GHz model with a Fusion Drive installed really shows the benefits offered by Apple's innovative hybrid solution. In our Xbench test, which looks at CPU and storage performance, the 3.2GHz model scored an impressive 199.50. But this score was trounced by the 3.4GHz Fusion Drive model, which managed 503.30. In a similar vein, the non-Fusion iMac's score using the Unigine Heaven 4.0 benchmarking tool was 501, but the iMac with a Fusion Drive and superior graphics scored 1165.
The benefits of upgrading to a Core i7 processor should not be overlooked either. Comparing the 3.4GHz Core i5 iMac we tested with a 3.5GHz Core i7 model, the Core i7 scored 17% higher in our Cinebench 3D rendering test with all available cores in play.
This is because although the processor is only 0.1GHz faster than the off-the-shelf Core i5, the Core i7 offers a Hyper Threading feature, whereby two threads can run on each of its four cores, for eight virtual cores.
Whatever the components and clock speeds, the new iMac is also gorgeous to use. The new screen offers excellent color reproduction and viewing angles, and it's a lot less reflective than pre-2012 models, which is important if you're working in an unevenly-lit room.
Its in-built speakers can't match a pair of quality external speakers, but they compare extremely well next to those offered by other monitors or all-in-one computers, and the new wireless ac compatibility brings faster, more stable WiFi networking to those with a compatible router.
iMac 27-inch, 3.2GHz quad core Intel Core i5, late 2013
Cinebench 10 Single core: 5925
Cinebench 10 Multi-core: 20244
iTunes encoding: 449.7 seconds (USB SuperDrive)
Movie encoding (iMovie): 127.5 seconds
Doom 3: 232.6 FPS
Call of Duty 4: 89.3 FPS
Unigine Heaven 4.0, FPS: 19.9
Unigine Heaven 4.0, Score: 501
NovaBench, Score: 993
NovaBench, Graphics: 259
iMac 27-inch, 3.4GHz quad core Intel Core i5, Fusion Drive, late 2013
Cinebench 10 Single core: 6250
Cinebench 10 Multi-core: 21481
iTunes encoding: 450.3 seconds (USB SuperDrive)
Movie encoding (iMovie): 114 seconds
Doom 3: 247.0 FPS
Call of Duty 4: 89.4 FPS
Unigine Heaven 4.0, FPS: 46.2
Unigine Heaven 4.0, Score: 1165
NovaBench, Score: 1177
NovaBench, Graphics: 402