How to disable monitor auto detection in Windows 7?

Question

I am currently running Windows 7 Ultimate 64-bit with a dual monitor setup with an NVIDIA 7950 GT graphics card. One monitor is dedicated to this machine and the other monitor is connected to a DVI KVM switch.

When I switch to my other computer, Windows 7 disables the monitor. However, when I switch back it does not re-enable the monitor. The only circumstance that automatically re-enables the second monitor is when I switch back after Windows has put the monitors into power save mode. I am continually having to bring up the NVIDIA control panel to have it re-enable the monitor.

Under Windows XP I would just disable the NVIDIA service to prevent it from auto-detecting the monitor (which doesn't solve the problem under Win7), and in Vista there was a registry hack that would prevent this. It looks as though that has been removed in Windows 7.

I have found similar questions posted on this site, but nothing that matches my problem exactly. The following link is the question that comes the closest, but does not provide a solution to the problem.

How do I fix monitor detection in Windows 7?

Is there a way in Windows 7 to disable monitor auto-detection?

Update: I just added a second graphics card to my Windows 7 64-bit machine. I plugged one monitor into each graphics card. Now, when I use the KVM switch to switch back and forth it will re-enable the second monitor like it should. There are however, a few quirks with this. If I have a program maximized on the second monitor and it has focus, when I switch it will move to monitor 1. If I have a program maximized on the second monitor and it does not have focus, when I switch it will behave like it is minimized and when I bring it back up it will show up maximized on monitor 1.

Definitely better than it was, but still looking for a way to disable the auto-detection.

Answer 1

Maybe this is too simple, but have you tried just using the windows+p hot key? That works only in windows 7, but is a quick way to extend, duplicate, or select a single screen. (note: when it says projector is means your secondary display)

If you're dealing with Windows Vista you can turn off Auto-Detect through following this guide. It is supposedly only for nvidia cards but may work for others as well.

That post says:

1. Open the Start Menu. A) Click All Programs -> Accessories -> System Tools -> Task Schedular.

OR

1. Open the Control Panel (Classic View). A) Click Administrative Tools -> Computer Management.
2. Click Continue for the UAC prompt.
3. In the left pane, expand Task Scheduler, Task Scheduler Library, Microsoft, Windows, and click on MobilePC.
4. In the middle pane, right click on TMM.
5. To Disable TMM - Click on Disable.
6. To Enable TMM - Click on Enable. NOTE: TMM is enabled by default in Vista.
7. Close Task Scheduler.
8. Logoff and logon, or restart the computer to see the change.

You can also do it directly from the registry:

Using Windows Registry Editor Open Windows registry editor(regedit) Navigate to this location

Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\TMM

Right click on the (UseIViewHelper) value and select modify. set the value data to 0 to disable TMM feature in Windows. If you want to re-enable TMM feature,set the value data to 1.

You also have to restart the PC afterwards.

reference

As far as windows 7 goes, it's not possible at the moment. According to moderators at microsoft's forums: "This behavior is by design and I don't think there is a way to override this functionality except to make sure that both monitors are turned on when you start the system." Pretty lame. Right now however there is a way to request this feature. Please go to the link and request this feature if you feel it is important. Also a ticket for the feature has been created officially as well. Only time will be able to tell.

A Third party software may be useful, but I have not personally used any for this purpose. I have found MultiMon which is built for multiple monitors. Hopefully this will be of some use until microsoft gets it right.

Answer 2

There is a piece of hardware can probably solve your problem.

The purpose of such a device is to sit in between the cable of your monitor and to make the computer think the monitor still exists. It does this by recording the EDID once and repeating it all the time afterwards.

• http://www.monoprice.com/Product/?c_id=101&cp_id=10110&cs_id=1011003&p_id=3048&seq=1&format=1
• http://www.gefen.com/kvm/ext-dvi-edidp.jsp?prod_id=4715
• http://www.gefen.com/kvm/ext-hdmi-edidp.jsp?prod_id=8005
• http://www.hdfury.eu/en/home/5-dr-hdmi.html
• http://www.aten.com/products/Video-Products/Converters/HDMI-EDID-Emulator~VC080.html

Answer 3

To disable monitor detection, with AMD/ATI gfx cards under Windows 7, search for DMMEnableDDCPolling registry key and set it to 0 (it is DWord). There are several places in the registry where this key is located. Change them all and reboot. Doing this will disable constant polling of the display driver to detect if user attached a monitor.

If you lack the entry, look for UMD keys under HKLM\SYSTEM\CurrentControlSet\Control\Class{4D36E968-E325-11CE-BFC1-08002BE10318}\ and add it to those.

Answer 4

Have a look at your services. I had a similar problem and disabled "AMD External Events Utility" and it stopped looking for the monitor. I think on my old system it was called "ati hotkey poller"

Answer 5

In case of NVidia card you need to disable "NVIDIA Update Service Deamon" services.

1. Run "services.msc"
2. Disable those services
   • Change execution to manual

Answer 6

I have a similar situation to you, except instead of a kvm I have my main system plugged in with DVI and the secondary on VGA. That way I use the monitor's input select.

If that's not good enough: What KVM are you using? Do you have the same problem if you unplug and plugin the cables? Does turning the monitor on and off get Windows to detect it?

Maybe you need a better kvm? (That makes both computers think they're connected to a monitor.)

Answer 7

The only thing I can come up with, which isn't a very good solution is to buy a better KVM.

My first old KVM had the exact same problem as you are saying. I upgraded to a brand new digital one and it basically emulates/fakes a signal, even when you are not on the channel.

Other than that, I have created a registry fix for you that should disable TMM in Windows 7.

Answer 8

Here's a solution that worked for me. Windows 7, NVidia Quadro NVS 295. But that's largely irrelevant.

The important part is, these are HP monitors EliteDisplay 241i.

Go to the on screen menu > Input Control > DP Hot-Plug Detection > switch it from Low Power to Always Active.

Doing this on both monitors has resolved the problem for me. I suspect other monitors will have similar settings.

Answer 9

Solution for (at least some) Nvidia cards. Better late than never I guess. For an Nvidia card (Quadro FX 1400, driver 9.18.13.908) using an Nvidia driver:

Right click on desktop
Select "Nvidia Control Panel"
Workstation -> view system topology
For the monitor in question click on "EDID"
Save EDID as text file.
Load EDID from text file (the one just saved).
Now EDID source is "File", previously it was "Monitor".

After doing this switching the KVM no longer altered the desktop.

It would probably be a good idea to switch it back to "monitor" before attaching a different display device!