I'm surprised nobody posted this, since it's already two weeks old, but BareFeats has provided us with some benchmarks of the iMac 5K 2017 with eGPUs. Yes, that's plural, since he tested with both a single eGPU and a dual eGPU setup.
http://barefeats.com/imac17egpu.html
GRAPH LEGEND
eGPUs>1080Ti*2>Built-in - Dual GeForce GTX 1080 Ti (11GB) GPUs one in the Sonnet eFGX Breakaway Box and one in the AKiTiO Node eGFX Box but using only the iMac 5K's built-in display.
eGPUs>1080Ti*2>Dell - Dual GeForce GTX 1080 Ti (11GB) GPUs one in the Sonnet eFGX Breakaway Box and one in the AKiTiO Node eGFX Box with one GPU connected by dual DisplayPort cables to an external Dell 5K display
eGPU>1080Ti>Built-in - One GeForce GTX 1080 Ti (11GB) GPU installed in Sonnet eFGX Breakaway Box but using only the iMac 5K's built-in display
eGPU>1080Ti>Dell - One GeForce GTX 1080 Ti (11GB) GPU installed in Sonnet eFGX Breakaway Box and connected with dual DisplayPort cables to an external Dell 5K display
eGPUs>RX480+580 - One AMD Radeon RX 580 GPU installed in Sonnet eFGX Breakaway Box and one AMD Radeon RX 480 GPU installed in the AKiTiO Node eGFX Box
eGPU>RX580 - One AMD Radeon RX 580 GPU installed in Sonnet eFGX Breakaway Box and connected with dual DisplayPort cables to an external Dell 5K display
Pro580 - '2017' iMac 5K with 4.1GHz Quad-Core i7, 64G of 2400MHz DDR4 memory, Radeon Pro 580 GPU (8GB VRAM), 1TB PCIe based flash storage
WHAT DID WE LEARN?
If you are using your iMac 5K to edit video with DaVinci Resolve, you can get a big boost with 1080p playback with Noise Reduction by adding an eGPU with a secondary GPU. However, there is little to be gained with playback or export of RED 4K/5K video since the on-the-fly decoding of RED is CPU intensive.
Did you notice that Resolve did playback and 'deliver' faster when we only used the iMac 5K's built-in display rather than the external Dell 5K display? On the other hand, you will find that with other apps, you must have the eGPU's graphics card directly connected to an external display before the external GPU(s) will be utilized.
LuxMark results reveal the potential of apps that can use multiple GPUs to render OpenCL based projects. Ditto for Blender. And the only way to add a second or third GPU on your iMac 5K or MacBook Pro is with an eGPU box.
The Blender test shows how one NVIDIA GPU rendering with CUDA is twice as fast as three AMD GPUs running OpenCL. And apps like Octane Render won't even function without CUDA capable GPUs.
http://barefeats.com/imac17egpu.html
GRAPH LEGEND
eGPUs>1080Ti*2>Built-in - Dual GeForce GTX 1080 Ti (11GB) GPUs one in the Sonnet eFGX Breakaway Box and one in the AKiTiO Node eGFX Box but using only the iMac 5K's built-in display.
eGPUs>1080Ti*2>Dell - Dual GeForce GTX 1080 Ti (11GB) GPUs one in the Sonnet eFGX Breakaway Box and one in the AKiTiO Node eGFX Box with one GPU connected by dual DisplayPort cables to an external Dell 5K display
eGPU>1080Ti>Built-in - One GeForce GTX 1080 Ti (11GB) GPU installed in Sonnet eFGX Breakaway Box but using only the iMac 5K's built-in display
eGPU>1080Ti>Dell - One GeForce GTX 1080 Ti (11GB) GPU installed in Sonnet eFGX Breakaway Box and connected with dual DisplayPort cables to an external Dell 5K display
eGPUs>RX480+580 - One AMD Radeon RX 580 GPU installed in Sonnet eFGX Breakaway Box and one AMD Radeon RX 480 GPU installed in the AKiTiO Node eGFX Box
eGPU>RX580 - One AMD Radeon RX 580 GPU installed in Sonnet eFGX Breakaway Box and connected with dual DisplayPort cables to an external Dell 5K display
Pro580 - '2017' iMac 5K with 4.1GHz Quad-Core i7, 64G of 2400MHz DDR4 memory, Radeon Pro 580 GPU (8GB VRAM), 1TB PCIe based flash storage
WHAT DID WE LEARN?
If you are using your iMac 5K to edit video with DaVinci Resolve, you can get a big boost with 1080p playback with Noise Reduction by adding an eGPU with a secondary GPU. However, there is little to be gained with playback or export of RED 4K/5K video since the on-the-fly decoding of RED is CPU intensive.
Did you notice that Resolve did playback and 'deliver' faster when we only used the iMac 5K's built-in display rather than the external Dell 5K display? On the other hand, you will find that with other apps, you must have the eGPU's graphics card directly connected to an external display before the external GPU(s) will be utilized.
LuxMark results reveal the potential of apps that can use multiple GPUs to render OpenCL based projects. Ditto for Blender. And the only way to add a second or third GPU on your iMac 5K or MacBook Pro is with an eGPU box.
The Blender test shows how one NVIDIA GPU rendering with CUDA is twice as fast as three AMD GPUs running OpenCL. And apps like Octane Render won't even function without CUDA capable GPUs.
