New iMac - GPU for Aperture with ext. monitor

Discussion in 'Digital Photography' started by jdavtz, May 8, 2011.

  1. jdavtz macrumors 6502a

    Joined:
    Aug 22, 2005
    Location:
    Kenya
    #1
    I'm thinking of upgrading my 2008 iMac C2D.

    Searching online for 6770m 6790m gives me nothing that I can make sense of about these GPUs. Anyone have a link with relative performances?

    I primarily use Aperture (21MP RAW files). Now I know that Aperture heavily uses the GPU, but I wonder just how much difference there is between the GPU models (and memory amounts - 512MB vs. 1GB vs. 2GB)

    I was thinking of 27" i7 3.4GHz with the 2GB card, but then wondered, "would I be okay with the 21.5" i7 2.8 with the 6770M GPU (with only 512 MB VRAM)".

    If I bought the 21.5" it would be much easier to afford a nice 27" NEC PA271W monitor (£1000-ish) (2560x1440) -- BUT would the 6770M/512MB GPU really be good for running moderately intensive Aperture work over the two screens (21.5" + 27")?

    Thanks for any advice/help! Jonathan.
     
  2. Ruahrc macrumors 65816

    Joined:
    Jun 9, 2009
    #2
    Probably not really enough to be important or even noticeable. Yes aperture uses the GPU but not nearly as much as everyone claims. I would argue that the same computer using something like a 320M and a 6970 would see similar performance in Aperture. It's still primarily dependent on CPU/memory performance, and after that, drive speed.

    Ruahrc
     
  3. Scuby macrumors regular

    Joined:
    May 16, 2010
    Location:
    Fareham, UK
    #3
    Aperture barely uses the GPU. I believe my iMac (late-2010, 21.5" base model) generally peaks at about 5-10% GPU usage when doing editing within Aperture.

    Fast hard drives (for browsing the library), fast processor (for edits) and lots and lots of RAM (for everything) will be much more beneficial.

    David
     
  4. toxic macrumors 68000

    Joined:
    Nov 9, 2008
    #4
    Aperture hardly uses the GPU. what it does use is video RAM, so get 1 GB if there's an option. 512 might cut it for one display, but not two.
     
  5. Ruahrc macrumors 65816

    Joined:
    Jun 9, 2009
    #5
    If it barely uses the GPU, it's barely using the GPU memory either. There will not be a noticeable performance difference between 512MB and 1GB video RAM in this case. System memory is what it needs, not video memory.
     
  6. toxic macrumors 68000

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    Nov 9, 2008
    #6
    it uses video memory. I verified this myself.
     
  7. Ruahrc macrumors 65816

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    Jun 9, 2009
    #7
    Sure, any application uses some video memory, but how much?

    As Aperture is not really loading massive amounts of polygon or texture data (like 3D games do for example), the amount of GPU memory it uses is pretty nominal. Consider that for basically all modern 2D display systems, the windows are treated as 3D "textures" with dimensions equal to their screen resolution (CoreImage). Even with 3x30" screens, the frame buffer usage is:

    2560x1600 pixels * 32 bits per pixel = 131072000 bits (divide by 8 bits per byte and that's 16384000 bytes or ~16MB)

    Multiply by 3 displays and you're still only at 48MB... a far cry from 512MB. Factor in a built-in overhead for overlapping windows, pop-ups, etc. and you've still got a long ways to go...

    Even if Aperture loaded a 21MP RAW file into GPU memory (which is unlikely as it is probably loading it into system memory instead), that's:

    21,000,000 pixels * 14 bits per pixel (usually for a high end RAW) = 294000000 bits (divide by 8 bits per byte = 36750000 bytes or ~37MB)

    You could easily load many times that quantity into video RAM and still have memory to spare... again on a 3x30" display setup.

    I just don't see where you are drawing your conclusions from. I would honestly like to know how you verified Aperture's GPU memory usage, I would be learning something new.

    Ruahrc
     
  8. toxic, May 9, 2011
    Last edited: May 9, 2011

    toxic macrumors 68000

    Joined:
    Nov 9, 2008
    #8
    I ran atMonitor while I edited in Aperture awhile ago just to find out, since there are others around the web who determined that VRAM is what Aperture really wants. GPU usage was normally less than 10%, and I don't think it ever went beyond 20 or 30%. VRAM could go to 80+% when using adjustment brushes. this was using a GTX 285 (1GB) on one display (1920x1200).

    I also had to deal with waiting a lot (more) after I upgraded to Aperture 3 while using an '08 MBP (6GB RAM, 256MB VRAM). 6GB RAM isn't ideal, but I didn't think it was the real bottleneck. that turned out to be CPU and VRAM.

    I can't get screenshots for you since atMonitor can only read NVidia GPUs for some reason. I just switched to an HD 5770.
     

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