The 'late 2015' 27" iMac 5K in several flavors when it comes to graphics processors. Readers ask, do I need the R9 M395X with 4G of VRAM? Or will the R9 M395 with 2G be sufficient? And what about the M390 and M380? Everyone's needs are different but here is the result of our efforts to test all options.

AFTERTHOUGHTS

We did our best to feature apps and benchmarks that stress the 'late 2015' iMac's various GPUs either exclusively or primarily. We didn't have the luxury of having the same CPU or storage on each. (Big mahalo to PowerMax for providing test units.)

LuxMark revealed some of the differences in the GPU specs. There is very little correlation between clock speed and performance. The M380's 1021MHz clock speed didn't help it keep up with the 909MHz M395X. However, the 32 compute units of the M395X did help it beat up on the M380's 12 compute units.

WHAT'S NEXT? CPU shootout between four flavors of 'late 2015' iMac and some 5120x2880 GPU results.

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