First Look: 2015 27-inch iMac Lineup Goes All 5K Retina

New Skylake Processors and Nimble Graphics

27-inch 2015 iMac with Retina 5K display
2015 27-inch iMac lineup goes all 5K Retina. Courtesy of Apple

Apple has updated the entire 2015 iMac lineup, including the first 21.5-inch iMac with Retina 4K display. The 27-inch iMac lineup, however, got the best of the updates. Gone are the non-Retina iMacs from the 27-inch lineup. If you're going big, you're going Retina; at least, that seems to be Apple’s take on the matter, and I tend to agree.

Ever since the 2014 27-inch iMac with Retina 5K Display was released, we knew that, just like the MacBook Pro lineup, which kept non-Retina models for the short term (in the 13-inch models), in the long term, Retina was the direction Apple would go across the entire product space.

So, besides the all Retina lineup, the 27-inch iMac received some significant updates that will please anyone looking to squeeze out more performance.

27-inch Retina Display With P3 Color Space

Let's start with the display. The 27-inch Retina display still comes in at 5K, with a 5120 x 2880 pixel resolution. The display still uses an IPS panel, but new for the 2015 model is a larger DCI-P3 color gamut. The P3 color space is larger, that is, it encompasses a larger color space, allowing not only additional colors to be displayed, but more vibrant colors as well. The P3 color specification is the same one used for digital movie theaters, and the projection technology used for modern motion pictures.

Apple’s adoption of a P3 color space for the new 27-inch iMac is very significant for those working in the motion picture industry, as well as anyone working in video production. As late as 2014, there was only a handful P3-certified monitors available to professionals, and at considerable cost, well above a fully tricked out iMac. So, you can see how the new iMac with a P3 5K display is going to be very attractive.


On the 27-inch iMac lineup, Apple skipped past the fifth-generation Broadwell processors, and went right to the most current Skylake models. The 2015 27-inch iMacs are outfitted with 3.2 and 3.3 Quad-Core i5 processors, with upgrades available to 4.0 GHz Quad-Core i7 processors. The i7-based models have the ability to run up to 8 concurrent threads, essentially mimicking the performance of an 8-core CPU.

The new Skylake processors don't provide a significant boost in performance over Broadwell-based models, but since Apple skipped over Broadwell, the Skylake processors should produce a nice jump in performance over the 2014 iMacs that used Haswell processors.

An additional benefit of the Skylake processors is that they're more energy efficient, running cooler while still providing a performance boost. When you have a massive 27-inch Retina display, keeping the insides of your Mac cool is an important consideration.


The 2015 27-inch iMacs use AMD Radeon R9 GPUs in three configurations: the R9 M380 with 2 GB of GDDR5 memory; the R9 M390, also with 2 GB of GDDR5 memory; and the R9 M395 with 2 GB of GDDR5 memory. There's also an option for an R9 M395X with 4 GB of GDDR5 memory.

Any of the AMD GPUs will easily drive the 5K display and still provide plenty of rendering muscle for most users. If you primarily envision using the iMac for image and video rendering, the R9 M395X with the larger memory may be of interest. But most of us, including those who may be wondering about game performance, should find the R9 M390 more than adequate.


The larger 27-inch iMac has some advantages just because of its physical size, which makes cooling the interior much easier than the 21.5-inch iMac models. One of these advantages is that even the baseline storage makes use of a 1 TB 7200 RPM drive. The faster rotation rate makes even the standard 1 TB hard drive used in the base model usable for most users.

If you step up to the mid or top tier models, you'll find a 1 TB Fusion Drive or a 2 TB Fusion Drive as the minimum standard. You can upgrade the base storage with larger Fusion Drives (up to 3 TB), or replace the drives with 256 GB, 512 GB, or 1 TB SSDs (depending on the iMac model).

One interesting change in the Fusion Drive configurations is that the 1 TB version has had its SSD component downsized from 128 GB to 24 GB. While this is still large enough to allow the OS and a few of your favorite apps to be stored on the fast SSD portion of the Fusion Drive, it obviously can’t store as many documents and apps as the previous version.

For casual users, I don’t see the change as being a negative. It actually reduces the cost of the Fusion option while still providing a hefty storage performance increase. Those who want to maximize Fusion performance can choose the 2 TB or 3 TB options, which still make use of the larger 128 GB SSD.


Thankfully, memory remains user upgradeable, which means you can configure your iMac with just the bare minimum RAM (8 GB), and upgrade the memory yourself, using less expensive third-party RAM. If you would rather have Apple add the RAM for you, it offers 16 GB and 32 GB upgrades.

The 27-inch 2015 iMacs make use of 1867 MHz DDR3 memory modules, and the iMac has four SO-DIMM user accessible memory slots (two are pre-populated for the 8 GB configuration).


The iMac retains the same connectivity options as the 2014 models. You'll find a headphone jack, SDXC card slot, four USB 3 ports, two Thunderbolt 2 ports, and a lone Gigabit Ethernet jack.

Wireless connectivity includes 802.11ac, Wi-Fi, and Bluetooth 4.0. 

iMac Base iMac Medium iMac High-End
Model # MK462LL/A MK472LL/A MK482LL/A
Processor 3.2 GHz Quad-Core i5 3.2 GHz Quad-Core i5 3.3 GHz Quad-Core i5
RAM 8 GB 8 GB 8 GB
Storage 1 TB hard drive 1 TB Fusion Drive 2 TB Fusion Drive
Graphics AMD Radeon R9 M380 AMD Radeon R9 M390 AMD Radeon R9 M395
Display Retina 5K 5120 x 2880 P3 Retina 5K 5120 x 2880 P3 Retina 5K 5120 x 2880 P3
Price $1,799.00 $1,999.00 $2,299.00
16 GB RAM +$200 16 GB RAM +$200 16 GB RAM +$200
32 GB RAM +$600 32 GB RAM +$600 32 GB RAM +$600
1 TB Fusion Drive +$100 2 TB Fusion Drive +$200 3 TB Fusion Drive +$100
2 TB Fusion Drive +$300 3 TB Fusion Drive +$300 256 GB Flash Storage no charge*
3 TB Fusion Drive +$400 256 GB Flash Storage +$100 512 GB Flash Storage +$200
256 GB Flash Storage +$200 512 GB Flash Storage +$400 1 TB Flash Storage +700
512 GB Flash Storage +$500 1 TB Flash Storage +900
4.0 GHz Quad-Core I7 +$300 4.0 GHz Quad-Core I7 +$250
AMD Radeon R9 M395X +$250
2015 27-inch iMac Configuration Chart

* 256 GB Flash Drive upgrade is in lieu of the 2 TB Fusion Drive


The base model of the 2015 27-inch Retina iMac has an attractive price, and unlike the base 21.5-inch iMac, uses a faster (7,200) RPM drive, and not the slower (5,400 RPM) drive commonly used in budget laptops.

The AMD Radeon R9 M380 doesn’t have the overall performance of the M390 or M395X offered in the other configurations, but it's quite capable of driving the iMac’s Retina display, as well as any other external 4K display you may hook up.

If you can swing the extra cash, the only upgrade I would recommend for the base iMac is the 1 TB Fusion Drive.

If you're looking for a bit more performance, my suggestion is to spend money on the i7 processor upgrade, to gain the hyper-threading support that allows up to 8 threads to run nearly simultaneously.

As for graphics, I can’t recommend the R9 M395X upgrade unless you have a specific application that can make use of the GPU’s additional onboard memory.

Published: 10/13/2015

Updated: 11/21/2015