The differences between the 660m 512mb and 755m 1gb

Discussion in 'iMac' started by xkmxkmxlmx, Feb 13, 2014.

  1. xkmxkmxlmx macrumors 6502a


    Apr 28, 2011
    I have searched the forums and the internet, but it still seems unclear to me. Can someone please breakdown what the differences are between the two base model cards?

    Can you expect to see any gains in gaming, for instance? And other general terms...

    Thank you.
  2. sahni130 macrumors 6502


    Jun 25, 2008
    Atlanta, Georgia, United States
    My knowledge is that the 755m is about 10-15% faster than the 660m, but the extra 512MB of gram definitely comes in handy for doing graphics intensive work. I was deciding between the same exact choices a month ago but went for the 660m because of the price/benefit ratio. With that being said if you can afford it, definitely go for the best you can afford. I read reviews on Anandtech, notebook check, etc etc. The $1399 refurb 27-inch iMac with 660m is not a bad deal I think. I have no problems running games like Call of Duty, Civilization V, etc with any problems on medium-high settings on my 660m. But if you want the best performance, and especially if you're doing serious gaming, you might want to consider the 680MX or the 780m.
  3. yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN
    To give you a general idea, the 1GB of GT750M in the high end 21.5" already outperforms a 1GB GTX660M (according to NotebookCheck). So the 1GB GT755M in the base 27" will definitely outperform the GTX660M even more.
  4. cirus macrumors 6502a

    Mar 15, 2011
    There is a minimal difference between the 750m and the 755m (mainly boost related).

    For PC clocks are (same chips)

    660m 950/1250 (core/vram) including boost
    750m 967/1250 (core/vram) + boost to (1058/1250).

    Thus the 750m is a good 11% faster (both with GDDR5).

    However, Apple disables boost on the 750m so it runs at 967/1250, pretty much identical to the 660m.

    512 MB vram is simply not enough for the 660m (really in apple's case 650m @ 900/1254) so the 750m should be faster in most cases.

    For example in a game such as Crysis 3, the 750m (GDDR5) can get around 40-45 fps at 1080p low (textures high and object quality high) and use over 1 GB vram.

    For comparison the 755m runs at 980/1350. Insignificantly faster.
  5. Jurisprudence macrumors member

    Dec 24, 2007
    512mb vram on any GPU for gaming these days is simply not enough. If you are gaming 1gb is essential, and an absolute minimum. At 512mb textures will have to be offloaded on to the much much slower main system ram bottlenecking the system. If you had a GTX780 TI with 512mb it would run like a crippled hamster.

    Up from there games such as Assetto Corsa (still in beta) are regularly reported to be taking 2.5gb vram and X-Plane will benefit from 4gb. Apart from those titles or The Witcher not won't benefit from increasing vram above 2gb.

    When I upgraded my iMac 2011 6770m 512mb to iMac 2011 6970m 1gb (different cards I know so not a direct comparison) I doubled my performance in general on titles such as BF3. On sims such as the DCS series which hates ATI cards & has a very old engine which doesn't take advantages of many features found in later GPU series I saw a similar doubling of performance, mostly due to the Vram doubling.

    OP: What games are you looking to play. There is a lot of BS out there on these issues but it would help to know.
  6. sahni130 macrumors 6502


    Jun 25, 2008
    Atlanta, Georgia, United States
    All of the above posters are correct. Simply get at least 1GB VRAM or more. If budget permits, why the heck not?

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