Is clamshell mode cpu more economical?

Discussion in 'Apple' started by dorayme, Sep 22, 2011.

  1. dorayme

    dorayme Guest

    Is clamshell mode cpu more economical or any other way more
    economical than leaving lid open and turning screen down to full
    dorayme, Sep 22, 2011
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  2. dorayme

    Alan Browne Guest

    I'd expect the machine would run a little cooler (more cooling area
    exposed) so the fan would not come on as often/as fast. Probably
    negligible in power terms.
    Alan Browne, Sep 22, 2011
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  3. dorayme

    dorayme Guest

    Yes, we have being surmising this in another thread. But the
    question is not about this.

    It is about the idea that if the lid is closed, is the video
    processing less, the external screen being the only one being
    used? With the lid open, I was imagining the video processing was
    distributing to the two screens, the external one being used and
    the blackened (the bright control down max) Macbook one not being
    dorayme, Sep 22, 2011
  4. dorayme

    Nelson Guest

    I don't think the brightness control changes the amount of processing
    the video processor and cpu have to do. It just changes how brightly
    the final result is displayed.

    I use a MacBook Pro as a dedicated "media center" driving an analog TV.
    At first, I thought clamshell mode was just the thing but I now leave
    it open all the time with the LCD screen on. It's much more convenient
    than screwing around with the bluetooth mouse and keyboard. And even
    though I know it vents through the back of the case, I observe that the
    keyboard and surrounding aluminum still get quite warm to the touch
    even in normal operation so when closed it must get warmer and cook the
    Nelson, Sep 23, 2011
  5. dorayme

    dorayme Guest

    Yes, one of my thoughts exactly. The other is that if the
    keyboard bright button is pressed enough, the video might be
    being turned off in a processing sense to the MB screen (as in
    clamshell, if indeed it happens in clamshell?). I simply do not
    know but there are two distinct ideas here, I do not know which
    applies or how they relate to the actual processes going on in
    these MBs.

    Very true, the keys are quite warm! Now that summer is coming
    here, I am leaving my MB open but except for some jobs, keeping
    its screen black. I miss having two big screens, the 13" is a bit
    small in any case, useful a bit for directories and pallettes but
    I will be glad of the day I get another modern Mac that will take
    two external screens (I think modern MBs can do this, certainly
    Minis can). My old QS Powermac could take a million screens...
    well, a few anyway, I once ran three on two PCI cards.
    dorayme, Sep 23, 2011
  6. dorayme

    Alan Browne Guest

    Brightness in the 'video' is an image issue. Processing.

    Brightness in the display is a hardware issue. Power.
    Alan Browne, Sep 23, 2011
  7. dorayme

    Alan Browne Guest

    Good questions. Perhaps the video card maker can answer that.

    You could always hack the power cord and put an ammeter coil around one
    of the DC leads ( + or return) to measure current in various conditions.
    Somebody you know probably has such an ammeter device to use with just
    about any hobby voltmeter or oscilloscope.

    (Some ammeter kits will also rectify around the AC but it will probably
    be less accurate due to conversion factors in the power adaptor and
    you'd have to hack a wire as well - though at least you could avoid
    hacking the nice white Apple power cord.)
    Alan Browne, Sep 23, 2011
  8. dorayme

    dorayme Guest

    Yes, I had the thought too that the two alternatives hypotheses
    would be testable in terms of gross power used by the MB over a
    period. But hard to arrange! One would need to compare the lid
    closed with the lid open over a set piece activity over the same
    period of time and the instruments would need to be pretty
    sensitive, fine-grained in resolution. Measuring the power
    perhaps and/or the heat generated!

    Actually, thinking aloud to you here Alan, there is obviously
    *something* quite different about the lid being closed when in
    actual clamshell mode. If you have the lid open with a window
    directory on the MB display (but not visible) and then close the
    lid, it goes into sleep mode. Wake and the directory then appears
    on a connected external screen. Move the directory window half or
    more off the external "onto" the *imagined* MB screen (there is
    no screen because the lid is closed). Open the MB lid. No matter
    what bright control key presses, no image appears on the MB. It
    seems the MB screen processing is cut off. Press Option Command
    Eject key (to sleep) and after minute or so Spacebar key to wake
    and the up the brightness and the part of the directory window is
    not visible.

    So, my guess is that clamshell is the more economical processor
    wise, probably power-wise too (in spite of screen black when lid
    open) but likely negligibly. But all is complicated by the
    greater heat load with the lid closed. Anyway, mildly interesting
    dorayme, Sep 23, 2011
  9. dorayme

    Alan Browne Guest

    No. If, as you surmise, the behavior of the video cards is different
    then the current draw change would be quickly apparent. Say it was a 2
    watt difference and the supply line is 18V, then you would see 111 mA
    difference immediately. (A bit more actually as that is prior to the
    power supply inside the unit).

    IOW you should see fairly discrete changes in current draw on each
    transition (if there is one).
    Milder than that.
    Alan Browne, Sep 23, 2011
  10. Just put in a bigger heatsink, right?


    Jeffrey Goldberg, Sep 23, 2011
  11. dorayme

    dorayme Guest

    A further thought Alan, I now think that one can be in a
    clamshell mode even with the lid open. So it is different to
    merely turning down the screen to full black.

    Clamshell mode with the lid up (to allow more heat to escape) is
    gottable as follows:

    1. Close the lid

    2. Make sure you go into sleep mode (Option Command Eject does it
    for me). You will see blank on the external screen.

    3. Wake the computer but not by opening lid. I do it via an
    external keyboard pressing space bar. You can also use a usb
    mouse I think, (mine is Bluetooth)

    4. Open the lid.

    And you should be in clamshell mode with lid open. Best of all
    possible worlds, especially for summer desktop operations.
    dorayme, Sep 24, 2011
  12. dorayme

    dorayme Guest

    Why the "just" when there are *much easier* options?
    dorayme, Sep 24, 2011
  13. dorayme

    dorayme Guest

    Milder than that.[/QUOTE]

    I take it that this remark is for brown-nosing TBG purposes.
    dorayme, Sep 24, 2011
  14. I think you may have started participating here after the heatsink wars.
    Let's just say that my "just" was in jest.


    Jeffrey Goldberg, Sep 24, 2011
  15. dorayme

    dorayme Guest

    Ah, an in joke?

    About jest, Jeffrey, an analogy: apart from Larry David, who has
    a clever way of comedy around the holocaust, most of us are not
    tempted to even try to be funny about it. It should be similar in
    respect to MB clamshell mode, it is too serious a subject.
    dorayme, Sep 24, 2011
  16. dorayme

    Paul Sture Guest

    Memories of a college disco. They started out using an old valve
    amplifier and a hair dryer with the heating element disconnected to keep
    it cool.

    As the first stereo disco in town (think Led Zeppelin) they became very
    popular and ended up with some very impressive kit. Heatsinks were
    _always_ on topic ;.)
    Paul Sture, Sep 24, 2011
  17. dorayme

    Alan Browne Guest

    True, and the LCD would draw more power than what would be saved by the
    fans not running.

    Unless there is a mode where the external screen is on and the lid
    screen is not backlit while open.
    Alan Browne, Sep 24, 2011
  18. dorayme

    Alan Browne Guest

    It's just not that interesting an issue.
    Alan Browne, Sep 24, 2011
  19. dorayme

    Nelson Guest

    A Kill-A-Watt meter would be easier and cheaper. They lend them out at
    the local library here for all the planet-savers to use :) I got one
    somewhere for around 6 bucks I think.
    Nelson, Sep 24, 2011
  20. dorayme

    Alan Browne Guest

    How fine is the watts or current resolution? (The co. brochures I've
    found online (w/o looking very hard) are mute on resolution/accuracy).
    Alan Browne, Sep 24, 2011
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