New 2015 5K iMac Running Slow? (FCX)

Discussion in 'iMac' started by Larrabee213, May 10, 2016.

  1. Larrabee213 macrumors regular

    May 27, 2009
    Hey, and thanks in advance for your help.

    I picked up the top end pre built 27" 5K iMac. 3.3ghz, 2Gb AMD, 2TB Fusion Drive, and also upgraded the ram to 16GB.

    I have been doing a bunch of work in FCPX today and it seems to run very slow. As does Compressor. Slower than my 2013 15" rMBP.

    When I look at the activity monitor, the CPU isn't even being used past 60%. About 35% is idle. Fans don't kick up either. IS there something up with my iMac?
  2. Samuelsan2001, May 11, 2016
    Last edited: May 11, 2016

    Samuelsan2001 macrumors 604

    Oct 24, 2013
    It is probably the fact that the i5 in the iMac doesn't have hyperthreading so it will be a bit slower than the hyperthreaded i7 in the rMBP for hyperthreaded workloads.

    It's slightly out of date but this gives you some idea on performance metrics.
  3. joema2 macrumors 68000


    Sep 3, 2013
    What task are you doing that's slow? Exporting to a file? Applying or rendering some effect in the timeline? What kind of camera, what resolution and codec?
  4. Larrabee213 thread starter macrumors regular

    May 27, 2009
    Most of the issues I am noticing are in FCPX. Just slow, lots of beach balls, even after allowing files to input and process. Surprised that the 2013 rMBP would be snappier. I guess that is all in the SSD vs the Fusion?

    And I guess things are going at a decent speed at export, more concerned that the system is not working as hard as it should if that makes sense.
  5. h9826790 macrumors G5


    Apr 3, 2014
    Hong Kong
    Depends on the video size / format, but sounds like Fusion drive create the bottleneck under real high demand.

    For export, if you utilise Quicksync, low system utilisation rate is expected.

    However, let's say you import a 4K video and add some effects. Both the CPU and GPU should work quite hard during rendering.
  6. joema2 macrumors 68000


    Sep 3, 2013
    It likely has nothing to do with SSD vs Fusion, nor i5 vs i7. I have both SSD and Fusion iMacs and have tested them extensively on many benchmarks, including various FCPX tests. There generally isn't a huge real-world performance difference and certainly not due to disk I/O. I also have a 2015 top-spec MBP with 1TB SSD and it's no faster than my 2013 iMac 27 with 3TB Fusion Drive on FCPX tasks.

    I have tested my i7 iMacs on FCPX by disabling hyperthreading with a special utility called "CPU Setter" and that only made about 30% difference and only on very specific tasks. An i5 would not account for a widespread general slowdown.

    You should not be seeing lots of beach balls (officially called the "spinning wait cursor"). That is a sign something isn't right, not just a slow app or task. E.g, intermittent hardware failure, non-responsive network I/O, old non-compatible FCPX plugin, disk space exhausted, editing media on a USB 2.0 HDD or thumb drive, etc.

    If you have any doubts about your Fusion Drive you can run the BlackMagic speed test and verify it is performing as expected:

    You can also run GeekBench to test general CPU performance:

    If you suspect a hardware problem you can run Apple Diagnostics. This is not comprehensive but sometimes finds obvious problems:

    Different codecs and resolutions can make a huge difference. E.g, H264 1080p on a MBP will be a lot faster than 4k on a top-spec iMac 27. Likewise some plugins like Neat Video noise reduction are very slow, esp. on 4k.

    Since FCPX has seamless built-in proxy support you can usually get faster performance by transcoding to proxy and setting the viewer to proxy. You must remember to set it back to original before final export. However on most Macs (including yours) it should not be necessary to use proxy to get good performance on most H264 1080p content.
  7. Samuelsan2001 macrumors 604

    Oct 24, 2013
    If you are getting beach balls etc then I revise my opinion it sounds like you machine has an issue.

Share This Page

6 May 10, 2016