iMac 2019 i9 slower at iMovie encoding than 2017 i5 3.8

Discussion in 'iMac' started by propower, Jul 15, 2019.

  1. propower macrumors 6502a

    Jul 23, 2010
    Got an i9 1TB SSD, 580X from the refurb store...

    First weird thing is I tested iMovie encoding. 4:30 video 1080p from H.264 footage - my i5 3.8 (running at 4.0GHz) 40G ram = 5:00, The new i9 8G ram running ~4.5GHz = 6:50 ... What??? Ran 4X - yep...

    The new one does Page out a few times where the 40G ram does not. Memory pressure is still less than 70% at all times. And I ran these tests on stock 2017 i5s and i7s in 2017 - was always very close with the i7 being slightly faster. The new i9 burns 2X the Watts - ramps fans to 2400 rpm at times and is almost 2 minutes slower... very unexpected - can't really buy more RAM just to try in it! The i5 ramps fans to maybe 1800 half way through. Fan much quieter than 2400 on the i9.

    Would 16 or 32G of RAM solve this or??
  2. whosthis, Jul 15, 2019
    Last edited: Jul 15, 2019

    whosthis macrumors member

    Aug 21, 2008
    Can you just put the RAM into the i9 and try it out? I *think* they work in the 2019, but only at 2400 instead of 2667 (which will be a rather insignificant slowdown). Not tested personally though.

    8 GB would not be something I'd like to use with this machine anyway. And another 32 GB cost next to nothing. What's the point of going i9 and then heavily limiting its usability? :)
  3. propower thread starter macrumors 6502a

    Jul 23, 2010
    The new machine is 2667 RAM - I was just reading about putting the old 32G 2400 RAM fro the old one into the new machine just to test - logical next step... By all the videos I watched this performance hit I am seeing does not track...

    If all goes well I will absolutely upgrade the i9 to 40G - just didn't want to hassle with possible RAM return on top of the iMac :)
  4. whosthis macrumors member

    Aug 21, 2008
  5. priitv8, Jul 15, 2019
    Last edited: Jul 15, 2019

    priitv8 macrumors 68040

    Jan 13, 2011
    On mine, I get these results:
    Source Clip: 5:38, 1080p, H.264, 17.7Mbps
    Project: no transitions, titles or other effects, just plain source file on timeline
    Faster Encode: 1:03
    Better Quality: 1:45
    Both create a H.264 file with 20Mbps bitrate.
    In both cases I see Quick Sync being used (GFX wakes up to 1.20GHz):
    Screenshot 2019-07-16 at 00.05.11.png Screenshot 2019-07-15 at 23.53.00.png
    PS the RAM I installed, is this from Crucial.
  6. propower thread starter macrumors 6502a

    Jul 23, 2010
    Put 32G 2400 RAM from other machine in and now get ~5:10 render. Really about the same as the 2017 580 now. I wish I could say exactly what the footage was but it is ~4:20 in iMovie. It encoding to 1080P (Better quality), Faster setting is 2:56. Couple of transitions and a title. Seems more in line - though I did think it should be 10% faster just from CPU speed. Could be an iMovie issue since cores are not being worked very hard :)

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5 July 15, 2019