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Mac OS Sierra and GPU Rendering

Now that it is release day, how does Sierra handle GPU rendering using Fractal Architect 4 ?

Fractal Architect is a hard core test for GPU compute drivers and seems to the best test tool available for GPU vendors to evaluate the quality of their driver/runtime APIs.

We tested with 5 different Mac configurations, and this is what we found (over 100 different Mac configurations have been released by Apple that have Metal/OpenCL compatible GPUs).

Evaluating Sierra Before Updating to It

You should evaluate Sierra with your favorite apps before committing to a full upgrade.

Doing a full Time Machine backup before doing a full upgrade is a very good idea. There is no easy way back to El Capitan, once you have committed to a full upgrade

You can install Sierra on to an external hard drive and then boot off that external hard drive to try it out. I recommend using a Samsung T3 Portable Flash SSD drive because of its great performance. Traditional external hard drives can be painfully slow.

Metal Rendering

Metal rendering on recent Intel GPUs works very well. Render speed on Intel Iris Pro close to that of AMD GPU on 2015 Macbook Pro.

2013 and earlier Intel GPUs have a compile problem  on Sierra, but not on El Capitan. 

If you only have a Intel GPU in your Mac, you will want to evaluate Sierra first (before upgrading to it), to see if your Intel GPU is compatible with Metal rendering

Metal rendering on AMD GPUs is much faster on Sierra than El Capitan.

Metal rendering on older 2012 Nvidia GPU works. Other years Nvidia GPUs were not tested.

OpenCL Rendering

OpenCL on older Nvidia and AMD GPUs works (unlike El Capitan where they were broken). On more recent GPUs, OpenCL works about the same as in El Capitan.

OpenCL on Intel GPUs still broken – but of course Metal can now be used on more recent Intel GPUs.

CUDA Rendering on Nvidia GPUs

CUDA does not work on any sandboxed app sold through the Mac App Store. Fractal Architect 4-CUDA adds CUDA as an alternate rendering platform. (It was written for users affected by the horrible Nvidia OpenCL drivers released with Mac OS El Capitan.)

Bad News for Sierra: Nvidia has not yet released usable CUDA drivers for Sierra. Stay on El Capitan if you need CUDA support.

Dual Metal GPU Rendering on 2015 Macbook Pro

For a laptop to offer dual GPU rendering, this is a big deal. You can render on both the AMD and Intel Iris Pro GPUs at the same time.

You could do this too on El Capitan, but the AMD Metal drivers are much faster on Sierra.

Dual Metal GPU Rendering on 2013 Mac Pro

This works very well.  Rendering video animations on this Mac is very fast.

Dual OpenCL rendering is not recommended due to a critical kernel dispatching bug present in recent versions of Mac OS. (Metal does not have this bug.)

Score:  Kickass with Caveats

Apple has clearly made a big effort to improve the Metal compute drivers for Sierra. OpenCL drivers (which had so many issues in EL Capitan) now seem to work as well as they did with Mac OS Yosemite.

Apple engineers actually found the cause of a bug preventing Metal rendering from working on Intel GPUs. We found the cause of a core bug in Metal preventing Metal Rendering on AMD/Nvidia. Hopefully, this collaboration can continue so Apple can achieve 100% rock solid GPU compute platform across all of its Mac configurations.

Probably 90% of Macs released in the last 3 years can now  use GPU rendering –( that is a guesstimate since we have no means to actually test 100 different Mac model configurations). This is a huge improvement over the El Capitan release, when we estimated then that only 30% of Macs could use GPU rendering.

We found issues on Sierra only with older Intel GPUs (i.e. 2013 Macbook Air). Workaround: Stay on El Capitan for now.

Intel CPU rendering has always worked. But when you can get 10x  faster rendering on a laptop with Metal, who wants to use CPU rendering ?

Meeting with Matt Feemster

Matt Feemster is the author of Fractorium, a GPU accelerated flame fractal renderer for Windows and Ubuntu Linux.

My son and I attended Nvidia’s CUDA conference and got to meet Matt since he lives in the Bay Area too.

The 3 Amigos – the only people on Planet Earth that have released apps that support GPU flame fractal rendering to date.

Left: Steven Brodhead Jr   – author of Flam4
Center: Steven Brodhead – author of Fractal Architect
Right: Matt Feemster         – author of Fractorium


OpenCl Rendering On OS X El Capitan

Lets be frank. Apple’s OpenCL drivers are in terrible shape in El Capitan.

On a 2015 Macbook Pro with AMD Radeon M9 370X GPU, renders are 45% slower than Yosemite 10.10.5. Metal is no alternative as its compilers can’t handle the app’s kernels on AMD GPUs.

On a 2012 Retina Macbook Pro with Nvidia 650M GT GPU, the OpenCL driver crashes the app in a function named LaunchGrid. In earlier OS X versions 10.7 through 10.10, the OpenCL drivers on this Mac were rock solid. Also Metal does not work for this GPU either.

OpenCL on Intel GPUs have never been able to compile the app’s kernels (except during Mavericks 10.9 Beta).  Metal does work on recent Intel GPUs, but a persistent GPU hang issue caused by that implementation, is a serius critical issue.

I apologize to my customers. I have no control over the quality of Apple’s OpenCL and Metal drivers.