iMac Retina 4K, Late 2015

The iMac "Core i5" 3.1 21.5-Inch Aluminum (Retina 4K, Late 2015/Broadwell) is powered by a 14-nm "Broadwell" Quad Core 3.1 GHz Intel "Core i5" processor (5675R). This CPU has four independent cores on a single chip, a 4 MB shared level 3 cache, and is paired with 8 GB of onboard 1867 MHz LPDDR3 SDRAM (upgradable to 16 GB at time of purchase, but not after). It also includes a 1 TB (5400 RPM) hard drive and an integrated Intel Iris Pro 6200 graphics processor that shares system memory. A "FaceTime HD" webcam and stereo speakers are built-in.

This model features a 21.5" 4096x2304 LED-backlit 16:9 widescreen IPS DCI-P3 "Retina 4K" display, which runs "pixel doubled" to look like 2048x1152. Its aluminum rear case is thicker in the middle and tapers to a razor-thin 5 mm at the edges.

Connectivity options include four USB 3.0 ports, dual Thunderbolt 2 ports, Gigabit Ethernet, 802.11ac Wi-Fi (802.11a/b/g/n compatible), and Bluetooth 4.0.

Compared to the model it succeeded, this version has a nearly identical external enclosure but is distinguished by a significantly higher quality and resolution "Retina" display, as well as a more advanced architecture and graphics architecture.

The "Late 2015" iMacs were bundled with a compact aluminum Apple Magic Keyboard and a choice of either a multi-touch "Magic Mouse 2" or a traditional wired Apple mouse. For an additional US$50, users could also upgrade from the Magic Mouse 2 to the "Magic Trackpad 2," which offers multi-touch and pressure-sensitive "Force Touch" capabilities.

The introduction of the Retina 4K display to the 21.5-inch iMac for the first time was the standout feature of this model, earning widespread acclaim for its stunning quality. The DCI-P3 wide color gamut was particularly praised by creative professionals working with photos and videos. The combination of a Broadwell quad-core i5 processor and the powerful integrated Intel Iris Pro 6200 graphics provided sufficient performance to drive the 4K display smoothly. However, the non-upgradable RAM was a significant point of criticism, making the initial purchase configuration crucial for future-proofing. The standard hard drive was also seen as a bottleneck, with many reviewers recommending an upgrade to a Fusion Drive.