Dell Precision M4600: Enabling Optimus disables LCD brightness control

Question

On my new M4600 I managed to install all drivers for the system. However, I noticed that after the Windows enters graphic mode (login screen), I am unable to change the LCD panel brightness.

The change display brightness slider in Windows 7 control panel does nothing. It is simply ignored. If I press Fn+Up or Down, the slider moves, but the brightness does not change. The Dell brightness OSD is displayed with the correct brigtness value, but it does not change (if I set the brightness to 50% before login screen at startup, this status displays 50% all the time).

I even tried installing official NVidia drivers, but the result is the same as with the Dell drivers.

neoto · Answer

I forgot: The OS is Windows 7 Enterprise 64-bit

AsH83 · Answer

I am having teh same problem with my M6600. Win7 64 bit

neoto · Answer

I took my laptop to Dell service and had to pay 1 service hour - they told me that I installed the drivers in the wrong order.

1. Install Windows

2. Install chipset drivers and restart

3. Install all other drivers

That's it. It worked for me.

MattnAZ · Answer

I just got off the phone with the Dell technician and he said that the brighness control is broken by design.

what I have found on my M4600 is that you can have either optimus on and multiple monitors, or optimus off and be able to brighten and dim the lcd display. but not both.

I have chosen multiple monitors. optimus on.

if you want to control the brightness of the lcd dispaly, then you can

uninstall the intel hd 3000 and the nvida quadro 1000m

reboot and go into bios and disable optimus save and reboot.

then download this driver

www.dell.com/.../precision-m4600

then install the driver and you should be able to brighten and dim the display, but only have 2 displays available.

-M

neoto · Answer

Well, I contacted the Dell service then and they figured out that I installed the drivers in the wrong order. I can't remember what is the right order, but the Optimus and brightness control does work with the integrated LCD.

However, I still have some issues with the brightness control - when Windows UAC screen is displayed and LCD is dimmed at level 2 (second lowest level), the screen is dimmed to lower level than 1 (the lowest) and stays there even after exiting UAC screen. Second problem arrises every time I use my Dell on batteries and allow it to turn off the display (monitor sleep). After waking up, the colors are all washed out until I open Start menu or switch between windows.

I haven't tried to flash BIOS yet, because I am afraid of the stability of the whole system.

I assumed that I will get a top-notch experience with 2000€ notebook... However, bulky case, loose display frame, driver problems, weird fan noises, soft case plastics, small touchpad... really can't allow to compare it with the **cBook Pros in the same price level. There are quite a few good sides also, but we usually notice the disadvantages first :)

paladin66 · Answer

The strange thing is that the LCD brightness control starts working AFTER the systems goes into hibernation and comes back out of it.

sokhornhout · Answer

yes that work for me too

SomeTechnician · Answer

Dear DELL, any plans to fix this?

paladin66 · Answer

Here is a solution that works, thanks to unknownusor http://commweb-ps3.us.dell.com/support-forums/laptop/f/3518/t/19438012 It worked for me.  Hope it works for you all as well. Thanks

SomeTechnician · Answer

Thanks Paladin66!

The registry changes mentioned on that site finally solved this issue for me too.

Double checked if Optimus is still on in BIOS, and it is.

So now finally LCD brightness can be changed using the Fn keys when Windows is running and Optimus is enabled.

Cheers.

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Dell Precision M4600: Enabling Optimus disables LCD brightness control

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