Turning off laptop display when external display connected with OS 10.6.3

What you consider a feature may have been considered a bug and fixed.
cooling with the lid closed and display off really should not be a big deal - and not helped much if at all by having the lid barely open.

You could get one of those USB cooling fan units to put under the machine to aide in cooling.

Or - though I have not tried this myself - you might be able to trick the machine into thinking that the lid is closed with a strategically placed magnet to trip the lid closed sensor and leave the lid wide open.

... I'd then open it a little bit to hit any of my laptop's key to turn on the external display only.

That's never been an approved procedure and I'm surprised it ever worked for you. It's not supposed to.

With the lid down, any type of USB activity will wake the MBP with only the external screen active. Typically this is done using an external keyboard and hitting the space bar. Mouse clicks from a USB mouse will also wake a sleeping system. But if you don't have an external mouse and keyboard, you can plug in any USB device, like a USB flash drive for instance, and that will cause the Mac to wake with only the external screen active. Once that happens, you can lift the lid as you have done in the past and the built-in screen will remain off.

I'm having the same issue also, except now then you try to wake up the notebook with the lid closed, it attempts to turn on the notebook screen. Then it immediately turns both displays back off.

Is there some other way to get full Resolution on the external screen while having a mirrored or "desktop" display??

Hi,

Just to understand this: is the only way to use the full resolution capaility of the external monitor to use the macbook with the lid closed, and having only the external monitor display the screen? And in order to do that, is the only way to FIRST put the MBP to sleep, and then turn it back on after the external display is attached? What about when switching back from the external display to the laptop? How do I avoid all this put to sleep and wake up stuff?

You can use the external display at its full resolution and the built-in display at its full resolution at the same time — but only in Extended Desktop mode, not in Display Mirroring mode. In mirrored mode, the external display is always limited to the same resolution as the built-in display.

To toggle from one mode to the other, press Command + F1.

BSteely,
On 10.6.2 everything has been working as you describe. After upgrading to 10.6.3 I am having 2 different behaviors. Always one of them can be observed at a time and for now it is seems random to me which one of them occurs.

To start with MacBook is in sleep mode, lid closed, external Dell 3008 connected with miniDP to DP cable
1. Either the MacBook Pro cannot be waken up from sleep with an eternal mouse at all
2. Or if it does wake up, it wakes up the screen as well, but within a second or 2 the MacBook falls into sleep again. Mouse can wake it up again, but the cycle goes on forever.

When the lid is open everything works like it used to in 10.6.2 in extended mode, but I have no way now to eliminate the laptop monitor and the mouse will always fall off the external monitor area into the laptop monitor even if I don't want to use the latter.

Do you have the MBP connected to its power adapter? What you describe sounds like what happens if the power adapter isn't attached.