Less than a year after the chassis overhaul that gave the iMac its new slimline bodywork, Apple's innovative desktop computer enjoys another revision. This time, it's a minor refresh, bringing Haswell processors, better GPUs and faster WiFi, but retaining the form factor of the previous generation. It's an unsurprising move.Last year's update had already radically redesigned the all-in-one Mac, dropping the optical drive in favour of a new slimline design with better speakers, a revamped and less reflective screen construction, USB 3.0 ports and a second Thunderbolt port. The upgrades for this year's model are all internal. If you were hoping for a Retina display, you'll be disappointed.Naturally, the iMac isn't the only slimline all-in-one computer out there.