The iMac “Core i7” 4.2 27-Inch Aluminum (Retina 5K, Mid-2017/Kaby Lake) technically is a “configure-to-order” configuration of the iMac “Core i5” 3.5 27-Inch (5K, Mid-2017) or iMac “Core i5” 3.8 27-Inch (5K, Mid-2017), but also is documented as a separate model for reader convenience. Other than processor (and the corresponding level 3 cache), this model can be configured identically to its stock brethren.
The iMac “Core i7” 4.2 27-Inch Aluminum (Retina 5K, Mid-2017/Kaby Lake) features a 14-nm “Kaby Lake” 4.2 GHz Intel “Core i7” processor (7700K) with four independent processor “cores” on a single chip, an 8 MB shared level 3 cache, 8 GB of easy to upgrade 2400 MHz DDR4 SDRAM, a 1 TB or 2 TB Hard Drive+SSD “Fusion” drive, and either a Radeon Pro 575 graphics processor with 4 GB of VRAM or a Radeon Pro 580 graphics processor with 8 GB of VRAM. It also has a built-in “FaceTime HD” webcam and stereo speakers.
This model has a 27″ 5120×2880 LED-backlit 16:9 widescreen IPS DCI-P3 “Retina 5K” display. The rear of the case is aluminum and is thicker in the middle and tapers to a razor thin 5 mm at the edges.
Connectivity includes four USB 3.0 ports, dual Thunderbolt 3 (USB-C) ports, Gigabit Ethernet, 802.11ac Wi-Fi, and Bluetooth 4.2.
Compared to its predecessor, this model essentially has the same external enclosure, but it has a more advanced processor and architecture, a faster video card, a brighter display, and Thunderbolt 3 (USB-C) ports.