Power users have grown to rely on graphics processing units from AMD, Intel and Nvidia to accelerate a wide range of computational functions – from visual effect filters to gaming and 360VR, and even to bitcoin mining. Apple finally supports external GPUs, which can easily be added as plug-and-play devices without any hack. Blackmagic Design just released its own eGPU product for the Mac, which is sold exclusively through Apple ($699 USD). It requires macOS 10.13.6 or later, and a Thunderbolt 3 connection. (Thunderbolt 2, even with adapters, will not work.)
The Blackmagic eGPU features a sleek, aluminum enclosure that makes a fine piece of desk art. It’s of similar size and weight to a 2013 Mac Pro and is optimized for both cooling and low noise. The unit is built around the AMD Radeon Pro 580 GPU with 8GB of video memory. It delivers 5.5 teraflops of processing power and is the same GPU used in Apple’s top-end, 27” Retina 5K iMac.
Leveraging Thunderbolt 3
Thunderbolt 3 technology supports 40Gb/s of bandwidth, as well as power. The Blackmagic eGPU includes a beefy power supply that can also power and/or charge a connected MacBook Pro. There are two Thunderbolt 3 ports, four USB3.1 ports, and HDMI. Therefore, you can connect a Mac, two displays, plus various USB peripherals. It’s easy to think of it as an accelerator, but it is also an appliance that can be useful in other ways to extend the connectivity and performance of MacBook Pros. Competing products with the same Radeon 580 GPU may be a bit less expensive, but they don’t offer this level of connectivity.
Apple and Blackmagic both promote eGPUs as an add-on for laptops, but any Thunderbolt 3 Mac qualifies. I tested the Blackmagic eGPU with both a high-end iMac Pro and the base model 13” 2018 MacBook Pro with touch bar. This model of iMac Pro is configured with the more advanced Vega Pro 64 GPU (16GB VRAM). My main interest in including the iMac Pro was simply to see whether there would be enough performance boost to justify adding an eGPU to a Mac that is already Apple’s most powerful. Installation of the eGPU was simply a matter of plugging it in. A top menu icon appears on the Mac screen to let you know it’s there and so you can disconnect the unit while the Mac is powered up.
Pushing the boundaries through testing
My focus is editing and color correction and not gaming or VR. Therefore, I ran tests with and without the eGPU, using Final Cut Pro X, Premiere Pro, and DaVinci Resolve (Resolve Studio 15 beta). Anamorphic ARRI Alexa ProRes 4444 camera files (2880×2160, native / 5760×2160 pixels, unsqueezed) were cut into 2K DCI (Resolve) and/or 4K DCI (FCPX, Premiere Pro) sequences. This meant that every clip got a Log-C LUT and color correction, as well as aspect ratio correction and scaling. In order to really stress the system, I added several GPU-accelerated effect filters, like glow, film grain, and so on. Finally, timed exports went back to ProRes 4444 – using the internal SSD for media and render files to avoid storage bottlenecks.
Not many applications take advantage of this newfound power, yet. Neither FCPX nor Premiere utilize the eGPU correctly or even at all. Premiere exports were actually slower using the eGPU. In my tests, only DaVinci Resolve gained measurable acceleration from the eGPU, which also held true for a competing eGPU that I compared.
If editing, grading or possibly location DIT work is your main interest, then consider the Blackmagic eGPU a good accessory for DaVinci Resolve running on a MacBook Pro. As a general rule, lesser-powered machines benefit more from eGPU acceleration than powerful ones, like the iMac Pro, with its already-powerful, built-in Vega Pro 64 GPU.
Performance by the numbers (iMac Pro only)
To provide some context, here are the results I got with the iMac Pro:
Resolve on iMac Pro (internal V64 chip) – NO eGPU – Auto GPU config
Playback of timeline at real-time 23.976 without frames dropping
Render at source resolution – average 11fps (slower than real-time)
Render at timeline resolution – average 33fps (faster than real-time)
Resolve on iMac Pro – with BMD eGPU (580 chip) – OpenCL
Playback of timeline at real-time 23.976 without frames dropping
Render at source resolution – average 11fps (slower than real-time)
Render at timeline resolution – average 37fps (faster than real-time)
Metal
Apple’s ability to work with eGPUs is enabled by Metal. This is their framework for addressing hardware components, like graphics and central processors. The industry has relied on other frameworks, including OpenGL, OpenCL and CUDA. The first two are open standards written for a wide range of hardware platforms, while CUDA is specific to Nvidia GPUs. Apple is deprecating all of these in favor of Metal (now Metal 2). With each coming OS update, these will become more and more “legacy” until presumably, at some point in the future, macOS may only support Metal.
Apple’s intention is to gain performance improvements by optimizing the code at a lower level “closer to the metal”. It is possible to do this when you only address a limited number of hardware options, which may explain why Apple has focused on using only AMD and Intel GPUs. The downside is that developers must write code that is proprietary to Apple computers. Metal is in part what gives Final Cut Pro X it’s smooth media handling and real-time performance. Both Premiere Pro and Resolve give you the option to select Metal, when installed on Macs.
In the tests that I ran, I presume FCPX only used Metal, since there is no option to select anything else. I did, however, test both Premiere Pro/Adobe Media Encoder and Resolve with both Metal and again with OpenCL specifically selected. I didn’t see much difference in render times with either setting in Premiere/AME. Resolve showed definite differences, with OpenCL the clear winner. For now, Resolve is still optimized for OpenCL over Metal.
Power for the on-the-go editor and colorist
The MacBook Pro is where the Blackmagic eGPU makes the most sense. It gives you better performance with faster exports, and adds badly-needed connectivity. My test Resolve sequence is a lot more stressful than I would normally create. It’s the sort of sequence I would never work with in the real world on a lower-end machine, like this 13” model. But, of course, I’m purposefully pushing it through a demanding task.
When I ran the test on the laptop without the eGPU connected, it would barely play at all. Exports at source resolution rendered at around 1fps. Once I added the Blackmagic eGPU, this sequence played in real-time, although the viewer would start to drop frames towards the end of each shot. Exports at the source resolution averaged 5.5fps. At timeline resolution (2K DCI) it rendered at up to 17fps, as opposed to 4fps without it. That’s over 4X improvement.
Everyone’s set of formats and use of color correction and filters are different. Nevertheless, once you add the Blackmagic eGPU to this MacBook Pro model, functionality in Resolve goes from insanely slow to definitely useable. If you intend to do reliable color correction using Resolve, then a Thunderbolt 3 UltraStudio HD Mini or 4K Extreme 3 is also required for proper video monitoring. Resolve doesn’t send video signals over HDMI, like Premiere Pro and Final Cut Pro X can.
It will be interesting to see if Blackmagic also offers a second eGPU model with the higher-end chip in the future. That would likely double the price of the unit. In the testing I’ve done with other eGPUs that used a version of the Vega 64 GPU, I’m not convinced that such a product would consistently deliver 2X more performance to justify the cost. This Blackmagic eGPU adds a healthy does of power and connectivity for current MacBook Pro users and that will only get better in the future.
I think it’s clear that Apple is looking towards eGPUs are a way to enhance the performance of its MacBook Pro line, without compromising design, battery life, and cooling. Cable up to an external device and you’ve gained back horsepower that wouldn’t be there in the standard machine. After all, you mainly need this power when you are in a fixed, rather than mobile, location. The Blackmagic eGPU is portable enough, so that as long as you have electrical power, you are good to go.
In his review of the 2018 MacBook Pro, Ars Technica writer Samuel Axon stated, “Apple is trying to push its own envelope with the CPU options it has included in the 2018 MacBook Pro, but it’s business as usual in terms of GPU performance. I believe that’s because Apple wants to wean pro users with serious graphics needs onto external GPUs. Those users need more power than a laptop can ever reasonably provide – especially one with a commitment to portability.”
I think that neatly sums it up, so it’s nice to see Blackmagic Design fill in the gaps.
UPDATE: The September 2018 release of Mojave has changed the behavior of Final Cut Pro X when an eGPU is connected. It is now possible to set a preference for whether the internal or external GPU is to be used with Final Cut Pro X.
Originally written for RedShark News.
©2018 Oliver Peters
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