iMac 5K (Late 2015) vs Mac Pro: 64GB Memory Supported

Get iMac 5K at B&H Photo and see also MPG’s computer gear wishlist.
See also diglloyd-recommended performance packages for iMac at OWC.

MPG recommends this iMac 5K: 27" Retina 5K Display, 4.0 GHz Intel Core i7 (Skylake), 1TB Flash, 8GB memory, AMD Radeon R9 M395X GPU (4GB GDDR5) + 32GB or 64GB OWC memory.

OWC 64GB Memory kit for late 2015 iMac 5K

All prior models of the iMac 5K have long been handicapped by a 32GB memory limit, thus forcing professionals to the Mac Pro.

But the late 2015 iMac 5K changes the game by accepting up to 64GB memory, which makes it far more viable for professional photographers like diglloyd, videographers, etc*.

For example, MPG digloyd’s everyday work cannot be done efficiently on a system with only 32GB memory, as the screen shot shows from a late-night image processing job. Observe that Photoshop CC is using 40 GB of real memory. This would be a serious performance problem on a system with only 32GB, yet with other apps also taking memory, even the 64GB system is stressed into using 7.8 GB of compressed memory, as shown.

Apple does not offer a 64GB memory option, but OWC offers a 64GB memory kit that costs only a little more than what Apple upcharges for 32GB, making an awesomely fast Photoshop or Lightroom workstation out of the late 2015 iMac 5K at a far lower price than the Mac Pro.

If the iMac 5K was bought with 8GB or 16GB of memory, here’s the cool thing: Apple now configures that 8GB as 2 X 4GB or 2 X 8GB, thus leaving two memory slots open. For a long time, it was 4 X 2GB or 4 X 4GB, occupying all four slots, so whatever came with the iMac had to be removed. So here’s what’s cool, if a full 64GB is not needed, keep the two modules that come with the 8GB or 16GB iMac 5K, but add 2 X 8GB or 2 X 16GB:

2 X 4GB + OWC 2 X 8GB ===> 24GB
2 X 4GB + OWC 2 X 16GB ===> 40GB
2 X 8GB + OWC 2 X 8GB ===> 32GB
2 X 8GB + OWC 2 X 16GB ===> 48GB

* Some iMac 5K drawbacks remain, name only two Thunderbolt ports (on one bus), which is problematic for multiple displays in particular, but also for multiple high performance devices, or device-to-device copies (bandwidth restrictions). Also, the Mac Pro can go to 128GB for really huge jobs.

Photoshop CC using 39.6 GiB of real memory, 7.8 GiB of compressed memory