2011 27" iMac triple monitor question.

Discussion in 'iMac' started by scottc, May 22, 2011.

  1. scottc macrumors newbie

    Jan 22, 2011

    I’m looking at buying a new 2011 27” iMac to replace my hackintosh.

    In my current setup I use two 22” monitors with a resolution of 1680x1050 at each monitor. The monitors both are HP model# w2207H and have HDMI inputs so a mini display to hdmi cable should work. My goal is to have a triple monitor setup with the iMac, a 22” monitor at each side of the iMac.

    My question is will the $1700 lower end 27” iMac with the Radeon HD6770M 512MB fulfill my needs and drive all the monitors?

    Or will the higher end $2000 iMac with the Radeon HD 6970 1gb work better? And why?

    I’m trying to save some money at first I was thinking about buying a mac mini, but I couldn’t sell myself on the Intel Core Duo. My current setup has an Intel Q8800 and 4 GBs of ram that now feels slow when compared to my 2011 2.2 GHz i7 MacBook Pro.

    So I’m guessing that the 2.7ghz Quad Core i5 that is the iMac will fulfill my needs.

    Ultimately what I really want the stability that you get from buying supported apple hardware. Lets just say my hackintosh is not completely stable.

    Additional info

    I’m not a gamer.

    With my current hackintosh I do the following things.
    • I server iTunes media to my apple TVs
    • Encode dvds and blurays with Handbrake and make MKV
    • DVR TV shows with eyetv3, then encode those shows for the apple TV.
    • And watch my IP based surveillance cameras

    Other than that it is just a basic home office machine. I just like to spread my work around.

  2. Vylen macrumors 65816

    Jun 3, 2010
    Sydney, Australia
    Each monitor you plug in ends up getting an even share of VRAM. So, 512MB/3 = 170mb each. Consequently, it should be a good idea to get the 1GB video card ;)
  3. alust2013 macrumors 601


    Feb 6, 2010
    On the fence
    That's not necessary for the work described. I run 2 displays with a 256MB card fine
  4. gcthompson macrumors newbie

    Apr 6, 2010
    Is it literally as simple as this? Does it not just take what is necessary? Say you are running a game on the main monitor is it limited to 170Mb of VRAM even though the other two aren't doing very much other than displaying a background and an email client?
  5. leman macrumors G3

    Oct 14, 2008
    Where do you have this information from?

    Each monitor needs only so much VRAM to store its state (for 1680x1050 this would be about 5-6MB). AFAIK, the remaining VRAM is just there for the taking, depending on what the software needs.
  6. gcthompson, May 23, 2011
    Last edited: May 23, 2011

    gcthompson macrumors newbie

    Apr 6, 2010

    This link seems to indicate that the memory is just a pool, it's not split up and enforced.

    The short answer is, it depends on how much total VRAM you'll need not how many monitors you have hooked up

    Incidentally - I have 3 displays, 1 x 1920 x 1080, 1 x 1680 x 1050 and the main monitor running at 2560 x 1440. I've happily run Left 4 Dead 2 on the main monitor at the full resolution and never experienced any issues. I've got the stock radeon with 512Mb VRAM
  7. gnasher729 macrumors P6


    Nov 25, 2005
    It's actually nonsense.

    Your video card will need either 10 or 12 bytes per pixel for each monitor itself (four bytes for what is displayed, four bytes for what will be displayed in the next frame, two or four bytes to keep track of what is in front of what), so in an extreme case of 2560 x 1600 x 12 bytes that's about 48 MB per monitor.

    The video memory also contains the contents of windows, whether visible or invisible, textures and so on. For that it doesn't matter how many monitors you have, but how many windows and how big. If the windows use too much memory, their contents can be thrown out and redrawn if needed; it doesn't matter on which monitor they are. And a window won't use 12 byte per pixel, more likely three or four.

    So in your example, two 30" monitors displaying each an email client only (one huge window covering the whole screen) will use maybe 60-70 MB each, not more.

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