Thunderbolt to HDMI - low res only?

Discussion in 'MacBook Pro' started by urimils, Aug 17, 2011.

  1. urimils macrumors newbie

    Aug 17, 2011

    Using the latest MBP 15", I'm connecting the mac to a projector via a monoprice Thunderbolt to HDMI adapter, and whenever I try to use a higher resolution the 1024x768(60 Hertz), everything on the screen lags, the mouse, movies, etc.
    Any idea what might be the problem?

    It was suggested that perhaps the monoprice isn't high-quality enough, but i don't wanna go around spending unnecessary $ without being certain.

    I would point out that a notebook PC, much older than my new MBP, but with a built in HDMI port, outputs 1600x1200 w/o a glitch.
    Needless to say, the projector supports full HD.

    Any ideas would be great :)
  2. ergdegdeg Moderator emeritus


    Oct 13, 2007
    Unless you have a faulty unit, the adapter should work. I'm using the same thing and my MBP can use an HD monitor without a problem.

    What model of computer do you have exactly and are you using mirrored mode?
  3. urimils thread starter macrumors newbie

    Aug 17, 2011
    MBP 15"
    2.3 GHz
    8GB RAM
    Antiglare version(hi res)
    with 6750M graphics

    anything else?

    not sure if I tried mirrored, but I did try using it as the only screen output(i.e. the macbook screen is off).

    I did notice some improvements when turning off background applications, but still, when playing movies(either with VLC or built in dvd player) there is a noticeable lag.
  4. snaky69 macrumors 603

    Mar 14, 2008
    Something is wrong with your machine or TV, I doubt it's the adapter.
  5. T4R06 macrumors 65816

    Oct 8, 2007
  6. urimils thread starter macrumors newbie

    Aug 17, 2011
    How can I test the various components?

    Is it possible the Raedon card doesn't kick in when needed?(is it needed for DVD viewing and such?)
  7. jimmie32 macrumors member


    Feb 11, 2011
    Beijing, CN
    Try gfxCardStatus (Google it) to manually switch to discrete.
    The adapter should technically work since even your old laptop worked. Try another HDMI adapter if the GPU does kick in. You might be wasting money, but you have to track down to whether its your Adapter or your MBP.

    It shouldn't be the GPU though. Even my old integrated Intel X3100 IGP could output full HD. As pointed by posters above, even if you are using the integrated GPU, the HD 3000 (as evidenced by the 13") is certainly capable of powering external monitors (or HDMI ports, in your case). :)

    Good luck!
  8. urimils thread starter macrumors newbie

    Aug 17, 2011
    The old laptop has an HDMI port on it, so no adapter was used.

    I guess i'll have to check a direct connection to some apple display, and see how that goes.

    many thanks to all of you :)
  9. alFR macrumors 68020

    Aug 10, 2006
    IIRC the latest MBPs always use the discrete GPU when driving an external monitor: the integrated card doesn't have a connection to the Thunderbolt port, apparently. Try using a known good adapter (if you can get hold of one) and cable to rule those out: alternatively, maybe get someone you know who has a 2011 MBP to come round and try their machine in your setup? If that's OK and the problem persists with your MBP I guess it's your machine.

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