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Re: iMac Pro thoughts

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Joe Marler
Re: iMac Pro thoughts
on Jun 19, 2018 at 2:12:19 pm

[Gabriel Spaulding] "... my 10-core iMac Pro had significant hardware issues Apple was unable to fix, then I upgraded to an 18-core iMac Pro that had the exact same problems. I returned that and now have a maxed out 5k iMac, and in nearly every case it is outperforming the 18-core iMac Pro. Multicam editing is smoother, playback is smoother, Motion render times are more or less identical...In fact, before I returned the 18-core machine I compared it to my late 2013 iMac: the 18-core with directly attached OWC Thunderbay 4 drives was MUCH slower at playback and export than the late 2013 iMac accessing media on the same drive... over a network..."

I've had two different 10-core Vega 64 iMac Pros and tested them extensively vs a 12-core D700 Mac Pro and a top-spec 2017 iMac. The results vary based on codec and workflow. Even the old nMP is pretty quick on ProRes. It is hobbled on H264 since it doesn't have Quick Sync.

While the iMP doesn't have Quick Sync, FCPX apparently uses AMD's UVD/VCE hardware so it's much faster than the nMP but no faster at encoding, editing or encoding H264 than a 2017 i7 iMac. In fact the iMac is smoother and faster on 4k H264 than a 10-core Vega 64 iMP.

The main problem with the iMac Pro is H264. It's faster than the "trash can" but that's a low bar -- the nMP is very slow on that codec. If I used an all ProRes or raw workflow I'd be happy with the iMac Pro.

The iMP might do better than the iMac on an effects-heavy timeline but it's difficult to know what effects use what % of GPU. Even effects which are frequently described as "GPU intensive" often don't use that much. This can be determined with various monitoring tools like the latest version of iStat Menus.

The BruceX test is GPU-intensive but is tricky to run to avoid caching, pre-rendering or codec effects. If exporting to ProRes 422 from an unrendered timeline using a fresh library, I got the following numbers:

2017 i7 iMac 27: 15.8 sec
12-core D700 Mac Pro: 17.0 sec
10-core Vega 64 iMac Pro: 14.8 sec

For those using an all-ProRes or RED RAW workflow the iMP is pretty fast. I didn't test those codecs vs the nMP but my impression is a 10 or more core iMP is faster.

Re I/O, I tested the iMP on many different Thunderbolt drive arrays and it did just fine, certainly no slower than the iMac.

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