SHOOTOUT: iMac Retina 5K
entry model versus top model
Posted Wednesday, October 29th, 2014 by rob-ART morgan, mad scientist
The iMac with Retina 5K Display comes in two CPU 'flavors': The quad-core i5 and quad-core i7. Both ship with the AMD Radeon R9 M290X GPU unless you specify the optional R9 M295X GPU. We had a brief encounter with the 'entry' i5 model. Here's a snapshot of how its CPU and GPU performance compares to the top i7 model with optional GPU.
GRAPH LEGEND
iMac 5K Quad i7 = 'late 2014' iMac Retina 5K 4.0GHz Quad-Core i7; Radeon R9 M295X GPU
iMac 5K Quad i5 = 'late 2014' iMac Retina 5K 3.5GHz Quad-Core i5; Radeon R9 M290X GPU
Cinebench R15 -- Render 3D Model using all cores. (RED graph bar means FASTEST CB Rating.)
Notice the gap widens from 13% to 47% when the Hyper-Threading of the Core i7 kicks in to simulate 8 cores.
LuxMark
This is an OpenCL benchmark. We rendered the Sala scene using GPUs only. The R9 295X GPU in the Quad-Core i7 displays a 15% advantage. (RED graph bar means FASTEST in Thousands of Samples per Second.)
The GFXBench 3.0 OpenGL ES 3 has a "T-Rex HD" test a game simulation where a Tyrannosaurus chases a dirt bike rider. The "OFF-screen" mode runs the test at 1920x1080 offscreen. Surprise, the R9 290X GPU in the Quad-Core i5 runs this test 6% faster. Hmm. (RED bar means FASTEST in Frames per Second.)
(NOTE: We didn't publish the results of the ON-screen test because it is VSYNC can't be disabled, limiting the frame rates to 60.)
INSIGHTS
The performance difference between the 'entry' iMac with Retina 5K Display and the 'fully optioned' iMac 5K is not extreme unless you are running apps that use all available cores. In the case of Cinebench's CPU Multi-Core stress test, the iMac 5K with the Quad-Core i7 CPU is 47% faster since it supports Hyper-Threading -- simulating 8 cores -- while the Quad-Core i5 with NO Hyper-Threading support 'limps' along with only 4 cores.
We were surprised to see the iMac 5K Quad-Core i5 with the R9 290X GPU beat the Quad-Core i7 with R9 295X GPU in the GFXBench 3 T-Rex test. Looking at the published specs, the M290X exceeds the M295X on core clock speed, boost speed, and pixel fillrate. So that might be part of the explanation.
Be sure to see our follow-up page with Real World benchmarks comparing the 'entry' and 'top' iMac with Retina 5K Display.
OTHER BARE FEATS ARTICLES ON THE iMAC Retina 5K
Go to our INDEX page for a list of several pages featuring the iMac with Retina 5K Display compared to other Macs.
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