What if the iMac Pro had
THREE Vega GPUs?
January 31st, 2018, by rob-ART morgan, mad scientist
February 5th - Corrected Blender results and displayed in seconds
We are excited that macOS 10.13.4 beta now supports hot-plug of eGPUs. That means no more logout/login when attaching the eGPU (aka eGFX) box. And macOS now recognizes the correct model name of the external GPU. In this case it recognizes we have Vega Frontier Editions mounted.
To celebrate, we connected TWO Sonnet eGFX Breakaway boxes to the iMac Pro's Thunderbolt 3 ports, each sporting a Radeon Vega Frontier Edition.
GRAPH LEGEND
Pro Vega 64, TWO Frontiers - The internal AMD Radeon Pro Vega 64 (16GB) GPU and dual AMD Radeon Vega Frontier Edition (16GB) GPUs were active. Each Frontier GPU was installed in a Sonnet eGFX Breakaway Box (650W*) and connected to the iMac Pro's Thunderbolt 3 ports (different controllers).
Dual Vega Frontiers - Two AMD Radeon Vega Frontier Edition (16GB) GPUs were active during rendering. Each was installed in the Sonnet eGFX Breakaway Box (650W*) connected to the iMac Pro's Thunderbolt 3 ports (different controllers)
Pro Vega 64, One Frontier - Both the internal AMD Radeon Pro Vega 64 (16GB) GPU and external AMD Radeon Vega Frontier Edition (16GB) GPU were active. Frontier is in Sonnet eGFX Breakaway Box (650W*) connected to the iMac Pro's Thunderbolt 3 port.
Vega Frontier - Only the external AMD Radeon Vega Frontier Edition (16GB) in Sonnet eGFX Breakaway Box (650W*) was active and connected to the Thunderbolt 3 port of the iMac Pro.
Pro Vega 64 - Only the internal AMD Radeon Pro Vega 64 (16GB) GPU was active.
(* We upgraded both Sonnet eGFX Breakaway Boxes with the Enermax ERV650SWT Revolution SFX 650W Plus Gold PSU recommended by Sonnet and honored by their warranty coverage. They will soon release a 650W version of the eGFX Breakaway Box.)
TEST MULE: 2017 iMac Pro 3.2GHz 8-Core Xeon W-2140B CPU, 32GB of 2666MHz DDR4 ECC SDRAM, 1TB PCIe based flash storage
LuxMark 3.1 OpenCL Test
In this two minute OpenCL benchmark lets you choose which GPUs will do the rendering. You can chose one or multiple GPUs as illustrated below. The LuxBall scene has 217K Triangles. (HIGHER KSamples per Second = FASTER)
The Hotel scene has 4973K triangles.
Blender 2.79 - Render Scene using GPUs only
This time we used the more complex Pavillon-Barcelona sample scene and specified rendering using GPUs in OpenCL mode. User Preferences allow you to chose which GPUs are active. (LOWER Time in SECONDS = FASTER)
DaVinci Resolve Studio 14.2 - Play while Rendering Noise Reduction
Using the Candle benchmark project, we playback a 1080p clip while rendering THREE noise reduction nodes on the fly. In Preferences > Hardware Configuration >GPU Processing Mode we chose OpenCL. GPU Manual Selection Mode enables you to chose which GPUs are active. (FASTER Frames per Second = FASTER)
WHAT DID WE LEARN?
There is much to be gained with multiple GPUs when running certain graphics intensive apps. We featured apps that not only use more than one GPU but also give you total control over which one and how many to use. Sadly, not every Mac app can use more than one GPU.
In each case, we used the Mac Pro's built-in 5K Retina display. Some apps ignore the external GPU unless you connect it directly to an external display and make it primary. But be aware that the performance of a faster external GPU can be hampered by the lower bandwidth of the Thunderbolt 3 connection compared to the internal GPU's connection.
We found this to be especially true of games, for example, which ran faster using the iMac Pro's internal Pro Vega 64 and internal display than when running on the Vega Frontier using an external Dell 5K display.
Once High Sierra eGPU support is available for NVIDIA Pascal GPUs, we will publish results for one or more of them connected to the iMac Pro via eGPU box.
NOTE: One reason we chose two Vega Frontier Edition GPUs for this eGPU test session is because the RX Vega 64 continues to struggle with Blender 3D render app.
Comments? Suggestions? Feel free to email me,
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