How to turn off display on iMac G5 (iSight)?

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brucemx5@yahoo.com - 28 Mar 2006 01:11 GMT

Is there an application or terminal command I can run that will turn
off or put the display to sleep on my iMac G5 (iSight) *but* keep
the computer running?

Yes, I know I can set the display to turn off automatically using the
Energy Saver preference panel. But I'm often running compression and
transcoding programs which keep the cpu at 100% for hours at a time,
and in this situation, my system never automatically sleeps.

And I really do want to turn off the monitor, not just run some
all-black screen saver that makes it look like it's off.

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void * clvrmnky() - 28 Mar 2006 17:51 GMT

> Is there an application or terminal command I can run that will turn
> off or put the display to sleep on my iMac G5 (iSight) *but* keep
[quoted text clipped - 7 lines]
> And I really do want to turn off the monitor, not just run some
> all-black screen saver that makes it look like it's off.

The LCD panel will go into a all-bits-off state when told to by the PMU.
There may be some current available to the inverter so it is ready to
turn on, but it always takes a few seconds for it to do that. This is
as off as it is going to get if you let the computer run all the time,
and it is certainly not a "all-black screen saver".

Only CRTs with various Energy Star rating support generally have the
notion of monitor off. This is because CRTs eat a fair amount of
current as long as the flyback transformer and electron gun is powered
up. This is not the case for LCDs.

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brucemx5@yahoo.com - 28 Mar 2006 18:17 GMT

> The LCD panel will go into a all-bits-off state when told to by the PMU.

I guess this is what I'm realy asking. How can I force the PMU to tell
the LCD panel to go all-bits-off, but keep the computer running?

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void * clvrmnky() - 28 Mar 2006 22:27 GMT

>> The LCD panel will go into a all-bits-off state when told to by the PMU.
>
> I guess this is what I'm realy asking. How can I force the PMU to tell
> the LCD panel to go all-bits-off, but keep the computer running?

VESA DPMS defines the 4 states for LCDs as they do for CRTs. The
question at hand is which of these states the Energy Saver stuff puts
the LCD into. I'm *guessing* it's D1/Standby or D2/Suspend.

Poking around in the Power Manager stuff shows that the ability to go to
Standby or Suspend will be used if the hardware supports it. There is
no Cocoa or Carbon control for DPMS Off/D3 (that I can find), which
makes sense since a CRT will not be turned off by my two G4s unless and
until the whole box is powered down. I suspect this is just the CRT
noting there is no signal at all and powering itself down.

However, my CRT goes into D2/Suspend mode because the hardware supports
it. This implies that in iMacs the LCD is either in D1 or D2. D3/Off
is not supported.

Note that if you have X11 installed, you can use xset to try and send
various DPMS signals to the X server graphics adaptor.

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brucemx5@yahoo.com - 29 Mar 2006 03:39 GMT

Thanks much for the tip. I fired up X11, and in the xterm window, tried
these commands in an xterm window:

xset +dpms
xset dpms force standby
xset dpms force suspend

And got back this error message:

xset: unknown option dpms

Looks like the DPMS option is not supported for xset on this iMac?
Sounded promising though.

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David Gimeno Gost - 31 Mar 2006 18:09 GMT

> Yes, I know I can set the display to turn off automatically using the
> Energy Saver preference panel. But I'm often running compression and
> transcoding programs which keep the cpu at 100% for hours at a time,
> and in this situation, my system never automatically sleeps.

I may be missing something here but... Isn't this precisely what the "Put the display to sleep when the computer is inactive" setting in the Energy Saver preference panel is for?

I mean, this setting will cause the system to turn the display off after the specified time of *user* inactivity, without the computer itself going to sleep at all if there is any *CPU* activity actually going on. Or am I misunderstanding what you want? Maybe this setting doesn't work for you the way it works for me?

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Alec McKenzie - 31 Mar 2006 18:50 GMT

My iMac G5 puts the display to sleep after five minutes, but
leaves the computer running all the time at 100% CPU.

All you have to do is go to System Preferences -> Energy Saver
-> Sleep, and set "Put the computer to sleep when it is inactive
for" to 'Never', and "Put the display to sleep when it is
inactive for" to five minutes (or whatever you want).

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Alec McKenzie
usenet@<surname>.me.uk

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Mac Forum / General / General / March 2006

How to turn off display on iMac G5 (iSight)?