It's no surprise that Apple plans to refresh its iMac range of computers this time of the year and since Intel Broadwell is not available in U-series flavor that can fit the iMac format, the refreshed models will get Haswell refresh processors.
This is not a huge leap forward from the current Haswell driven processors, but the 27 inch iMac will get a 5120x2880 5K screen and new AMD graphics.
Current generation iMac 27-inch computers start at $1,790 and come with a 3.2GHz quad-core Intel Core i5. Nvidia GeForce GT 755M with 1GB or 2 GB of video memory deliver the eye candy. The more expensive iMac SKUs currently feature GeForce GTX 780M 4GB GDDR5 graphics.
5120x2880 boasts 14.7 megapixels per frame
With a 5120x2880 5K screen you have to render 14,745,600 pixels which is significantly more than 8,294,400 pixels on a 3840x2160 UHD panel and you need faster graphics. Nvidia's Kepler architecture based GeForce GT 755M did a good job for the current generation and 2560x1440 panels, but it will reportedly be swapped for AMD graphics.
The new 5K iMac should come with a Haswell refresh Core i7 4790K with a 4GHz Turbo clock and you can bet that Intel is working on a Broadwell / Skylake version for 2015, as these CPUs bring less power consumption and faster performance at the same time.
Important design win for AMD
The 21-inch models will apparently stick with 1920x1080 panels and they currently use Intel HD 5000, Iris Pro or Geforce GT 750M graphics. We wonder if we will see a GPU change in 21-inch Macs as well.
The 27-inch 5K design win will be important for AMD, as the company gained a lot of positive coverage from its Mac Pro design win and apparently there will be more AMD graphics in Apple products, beyond the professional segment.
The new 27-inch iMacs are expected this fall running OSX Yosemite.