9400M is not turned off in "Highe Performance" mode

[wbyung]

I have found the following power usage stats from iStats menu bar in "Higher Performance" mode.

GPU1 2.06W
GPU2 2.97W

The readings were taken while it is idling.

I do suspect that switching from "Better Battery Life" would just "turn on the 9600M GPU and that there is no implementation in the ASIC to turn off the integrated graphics portion within the chipset.

 

[Quu]

Its impossible to turn the 9400M off as it is not only a GPU but also a system Chipset. If the 9400M turned off your laptop would also turn off as there would be nothing to link the CPU to the RAM the Hard Disks or any other component.

What is more likely is when you select the 9600GT the 9400M goes in to a low power mode or shuts off some of its Shader Cores that drive the GPU portion of the chipset.

 

[J the Ninja]

Also, read this:

http://www.nvidia.com/object/hybrid_sli_notebook_tech_overview.html

In the standard dual-GPU setup, the display is supposed to always remain attached to the IGP. I'm not sure Leopard actually does it this way though. (System Profiler seems to say the 9600 drives the display directly when it is enabled).

In any case, what Quu said is the main reason.

 

[alphaod]

Also if you turn off the IGP, then hybrid SLI wouldn't be possible.

 

[Abstract]

Its impossible to turn the 9400M off as it is not only a GPU but also a system Chipset. If the 9400M turned off your laptop would also turn off as there would be nothing to link the CPU to the RAM the Hard Disks or any other component.

Exactly.

This is the same old integrated graphics Apple (and other companies) have used in the past. The benefit of this new integrated graphics is that it has the power of a separate 9400 M video card from Nvidia.

If it was a discrete graphics card, then I guess they'd be able to shut it off.