[macdummy]

I recently got a hand me down dual 2.0 g5 tower for my work. I also have 2 displays that I use with it which is great.

My question is, is there a way for os x to not 'see' the second display when I don't want to use it even though it is plugged into the video card? Having both displays plugged in is ideal of course, but sometimes when I have free time to play a game, I'd like to have os x just not see the 2nd display and only recognize one. so i usually unplug my smaller display when i play a game.

The reason is I notice in system profiler that when two displays are plugged in, the vram is split in half. I'm wondering does this mean when i play a game (civilization 3 complete which I just bought and am addicted to) it only gets half the power from my video card?

is that how os x handles dual displays in relation to the video ram?

thanks

[waffffffle]

Kill the power on the second screen.

[FireWire]

I've been wondering the same thing, as I planned to add a second monitor to my 17" G4 iMac, with the help of the screen spanning hack. I would only need it occasionnally, and thus wouldn't want to compromise the video memory all the time, especially with Tiger installed.

As I doubt the process of plugging a display is "hot-swappable" (I think you have to restart?), would turning off the second display reallocate the VRAM to the main display dynamically? I'm asking this because I remember back in the time, if you didn't boot your computer with a monitor attached, the video drivers would not even load in the operating system, and the screen would display nothing if you plugged one after the computer was started (and you got a blank screen if you tried to remote-control your mac from afar!). You had to use a device like the gHead to boot a Mac headless. So maybe if the computer detects two display at startup, the VRAM will already be allocated accordingly?

[JKT]

The process of adding a second display is hot swappable. You don't need to restart - but you may need to flip your display preferences to get the second monitor seen.

[macdummy]

i've tried the unplugging the 2nd display from wall socket, yet when i click on my display preferences that i have set up in the menu bar, it still sees the 2nd display.

i guess the real nuts and bolts question is, if display preferences always 'sees' the 2nd display whether it's plugged in to the wall or not, does OS X automatically allocate VRAM to the 2nd simply because it's video connecter is plugged into the card?

i have a feeling that because it is still recognized, OS X will still give it some VRAM.

[JKT]

You just need to toggle the "Detect Displays" option to stop the second display from being "seen" after it has been switched off.

[Tyre MacAdmin]

I'm not sure if the low level hardware semantics change if you just unplug a monitor... meaning the video card re-adjusts and now allocates all the ram to the first display. But if you were to unplug the second monitor and reboot it would for sure.

[jasong]

You definitely do not need to reboot, just select Detect Displays from the menu extra or click the Detect Displays button in the Displays control panel.

What's interesting is that when I plug my HDTV into my powerbook via DVI, it automatically recognizes that I have added a display, but does not notice when I remove it.

[Goldfinger]

Originally Posted by jasong

You definitely do not need to reboot, just select Detect Displays from the menu extra or click the Detect Displays button in the Displays control panel.

If I shut down my second monitor and press the detect displays button nothing happens. It still thinks that I have 2 displays connected.

[analogika]

wehat happens if you actually disconnect it from the grafx card?

[Detrius]

Originally Posted by JKT

The process of adding a second display is hot swappable. You don't need to restart - but you may need to flip your display preferences to get the second monitor seen.

This depends on the video card. On newer cards, it works fine; older ones it works, but it's a hack, and even older cards it doesn't work at all.