iMac Pro – first week

About 8 month ago I started investigating to jump ship from Mac to PC for my grading machine. I have been using an iMac 3.5GHz i7 with GTX 780M from 2013. After many investigations I found it a difficult choice since I write software for Mac which I use daily on my grading machine. The other reason is Prores, which is what I deliver to 99% of my clients.

I started making some phone calls to see what was around and then the day came when Apple announced they would ship a new iMac Pro in December. So I decided to wait.

The day finally came when I could order my new grading machine and a few days ago I got it.

I decided to go for the 10 core version, which made most sense price wise and also since DaVinci Resolve is not relying on processor as much as on GPU.

Setup

I decided to “partition” my 2TB SSD with APFS Volumes. The nice thing with Volumes is that you can share all available space between the Volumes. Normal partitions are a fixed size, but APFS Volumes grow the more you put in them as you can see below.

I created a CACHE volume (which I limited to 1TB max size). This is used when Caching nodes or footage that is to heavy to play from my RAID. 1TB is enough to us it on several projects in Prores4444XQ HDR. And the speed of the internal SSD is hard to compete with. 3GB/s write and 2,5GB/s read is enough for the most demanding formats.

As for setup I have 2 negative things.

Dongles

I had to buy 2 dongles from Thunderbolt 3 to 2. One for my RAID and UltraStudio Mini Monitor, and one for client who come with Thunderbolt 2 drives.

Keyboard & mouse

Black is nice, but not on a keyboard without illumination when you sit in a dark grading room. So I will be using my old white USB keyboard a bit longer and my colleague is happy he got a cool black keyboard.

And Apple… your mice suck! Back to my trusted Logitech.

Speed

One of the first things I did after installing Resolve was to run the Candle test project to see how fast the GPU is.

The test applies Temporal Noise Reduction and Blur nodes to an HD image. Then when you play you can see if it plays back at full speed 24fps or not.

I did the tests in both Auto, Metal and Open CL settings for the GPU. I started with Auto and got very strange results.

TNR – 24, 22, 12, 8 fps

Blur – 16, 9, 5, 3 fps

But after I had tested Metal and Open CL, I returned to Auto and I got the same results as Metal. I could not recreate the low fps and I don’t know if this could be a Resolve issue.

The results I got including comparison with other setups:

Temporal Noise Reduction

Test iMac Pro (Metal) iMac Pro (Open CL) Mac Pro MacBook Pro (eGPU) iMac
1 TNR 24 24 24 24 22
2 TNR 24 24 21 24 11
4 TNR 18 14 11 19 6
6 TNR 12 10 7 12 4

Blur

Test iMac Pro (Metal) iMac Pro (Open CL) Mac Pro MacBook Pro (eGPU) iMac
9 nodes 24 24 24 24 13
18 nodes 24 24 21 24 7
30 nodes 17 17 18 24 4
66 nodes 8 8 8 15 2

iMac Pro (Metal) – GPU settings in Resolve set to use Metal
iMac Pro (Open CL) – GPU settings in Resolve set to use Open CL
Mac Pro – 2013 Mac Pro with 2xD700, 2,7 GHz 12 core Xeon X5
MacBook Pro (eGPU) – Macbook Pro late 2016, 2,6 GHz i7 with Sonnet TB3 eGPU box with Nvidia 1080Ti
iMac – my old iMac 2013 with GTX 780M

As you can see, the Vega 64 is comparable with the 1080Ti in an external box.

I am a bit disappointed that the speed isn’t faster, but this is just a test. Let’s see how it’s in real life.

DaVinci Resolve

I have now graded my first project in Resolve and it went very smooth. It’s nice to add some noise reduction and just press play. But I still needed to cache some nodes, because if you have the power you are going to do more things. I needed to add some sharpen plugins and other things to some shots. So the extra speed helps me make a better end result, but I guess you never can get enough GPU power.

When I rendered to HD Prores 4444 I got about 120fps, which is about 3 times the speed I got with my old iMac.

Premiere Export

Doing a 1 hour 35 minute feature film Vimeo Export (1 VBR) is almost twice as fast. From 1h 20 min to 45 min.

Verdict

Well I am happy with my new grading machine and I am looking forward to test the 10Gbit network interface in a few weeks time. Is it worth the money? In my case it is, since I can continue using macOS. But if you just want to have a lot of GPU power then this isn’t the machine for you.

 

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