How about TWO eGPUs connected
to one 2016 MacBook Pro?
Posted April 17th, 2017 by rob-ART morgan, mad scientist
Since there are two Thunderbolt 3 buses on the 2016 MacBook Pros and we have at least two eGPUs, we figured "Why not connect one on each bus and see what happens?" Also, how does it stack up against two different Mac Pros using the same GPUs?
GRAPH LEGEND
rMBP>eGPUx2 V2 - NVIDIA GTX GeForce 1080 Ti GPU in the Sonnet eFX Breakaway Box connected to a right side Thunderbolt 3 port and NVIDIA GTX GeForce 1080 GPU in the AKiTiO Node eGFX Box connected to a left side Thunderbolt 3 port of a 2016 MacBook Pro 15-inch
cMP>Dual 1080s- Dual NVIDIA GTX GeForce 1080 GPUs in x16 Slots 1 and 2 of the Mac Pro tower
rMBP>eGPUx2 V1 - NVIDIA GTX GeForce 1080 GPU in the Sonnet eFX Breakaway Box connected to a right side Thunderbolt 3 port and NVIDIA GTX GeForce 1080 GPU in the AKiTiO Node eGFX Box connected to a left side Thunderbolt 3 port of a 2016 MacBook Pro 15-inch
cMP>1080Ti - NVIDIA GTX GeForce 1080 Ti GPU in x16 Slot 1 of the Mac Pro tower
rMBP>Break>1080Ti - NVIDIA GTX GeForce 1080 Ti GPU in the Sonnet eGFX Breakaway Box connected to the Thunderbolt 3 port of a 2016 MacBook Pro 15-inch
nMP>Break>1080Ti - NVIDIA GTX GeForce 1080 Ti GPU in the Sonnet eFX Breakaway Box connected to the Thunderbolt 2 port of a 2013 Mac Pro
Blender - This is a free, open source 3D renderer. You can select either CPU or GPU. If you select GPU, you can choose either CUDA or OpenCL. You can also designate one or more GPUs. We rendered the BMW GPU Benchmark sample posted in their Demo File section.
(LOWER time in SECONDS = FASTER)
Octane Render - It only runs if there is one or more CUDA capable GPUs present. You can download the demo along with simple test scenes like the Benchmark Scene we used.
(LOWER time in SECONDS = FASTER)
DaVinci Resolve - Playback 1080p clip while rendering a single Noise Reduction node on the fly. We imported the popular Candle project.
(HIGHER frames per second = FASTER)
DaVinci Resolve - Playback with no effects of a 5120x2160 RED clip.
(HIGHER frames per second = FASTER)
WHAT DID WE LEARN?
Two eGPUs (and two NVIDIA GPUs) are clearly better than one for multi-GPU 'aware' apps like Blender and Octane Render. And eGPUs running half to one-fourth the bandwidth of the x16 PCIe 2.0 slot of the Mac Pro tower don't seem to suffer.
We don't yet have a second GTX 1080 Ti but one has to wonder what a matched pair would do.
DaVinci Resolve is another story. "Pinched" Bandwidth of Thunderbolt 3 and Thunderbolt 2 clearly slows down the "render noise reduction during playback" frame rate of the Candle test.
And with the RED 5K "Playback without effects" test, the bandwidth restriction is compounded by the need for the CPU to decode RED video on the fly. There is only so much impact a faster GPU has when it must wait for the CPU to do its thing.
NOTE: The Sonnet eGFX Breakaway Box we used is a soon-to-be shipping Thunderbolt 3 eGPU. More details when it is shipping. FYI, the price for an empty Breakaway Box will be $299.
WHERE TO BUY NVIDIA GEFORCE GTX 1080 Ti AND OTHER PASCAL 10 SERIES GPUS
B&H Photo Video has the GeForce GTX 1080 Ti Founders Edition. (Search their site for other models of Pascal 10 Series GPUs.)
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