Mac OS forum


VRAM ques. when using and multiple monitors

I'm using OS X 10.8 with two large LCD monitors (Apple and Sony).

My 27" iMac came with 512 MB of VRAM.

If the secondary monitor is turned off is there still only available 256 MB of VRAM available for my primary monitor.

I suspect that's the case and that my secondary monitor would have to be detached for my primary monitor to take full advantage of the 512 MB, but... can someone confirm this?

Also just curious... is there any kind of hardware that can be simply switched that would act as if my secondary monitor is unattached if this is the case. This would certainly be easier than having to unplug it.

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All Answers

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That's an interesting question

In reply to: VRAM ques. when using and multiple monitors

and deserving of an answer.
Unfortunately I do not have one but, creating a shortcut (alias) to the Monitors system preferences control panel might be just as quick as turning the second monitor off.
Then you know that all the 512MB is going to the one monitor.

Thinking this through though, with both monitors turned on, the System Preferences/Displays will give you the option of having two monitors displaying video.
With one monitor turned off, does the same system preferences pane now NOT see a second monitor and remove the dual display function from the Display system preference.

It does on my iMac, via a thunderbolt connection, which would indicate that all the VRAM is available to one monitor if the system does not detect a second monitor.


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Mine gives not such option

In reply to: That's an interesting question

My 27" iMac (mid-2010) running OS X 10.8 gives no such option to remove the dual display function (unless by this you are referring to 'mirroring').

However mirroring still requires the card to push two monitors.

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I'll check that again but

In reply to: Mine gives not such option

I am reasonably sure that with the monitor connected but off, I no longer get any Dual Monitor options in System Preferences.

I'll check it today sometime and get back with you


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I just checked and...

In reply to: I'll check that again but

I just checked as to whether my secondary monitor is seen by my system if it is turned off after booting or if it is seen if I boot with it first turned off.

In both cases my secondary monitor is seen.

If the Displays preference panel is opened it still shows my secondary monitor in the Arrangement tab so the system is seeing it.

This makes sense though since if the secondary monitor was turned on AFTER the system was booted the system would need to be ready for it.

Sadly I think the only way the 512 MB of VRAM can be focused on the primary monitor is to disconnect the secondary monitor.

If anyone can think of an easier way... please let me know.

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