KVM switch + Windows 7 creates monitor switching nightmare

Hi all,

My story is similar to most others, got a noname KVM switch, old faithful CRT monitor, XP box that works just fine, and a W7 box that is stubbornly stuck at 60Hz. Googled for answers and found threads like this, but no solutions, just annoyed users like me and canned answers that were abrasive and useless.

After trying most everything with no success I found this doc about overriding EDID on MS site:

http://www.microsoft.com/whdc/device/display/edid_over.mspx

I wondered if it could possibly work if there is no EDID at all, tried it, and the bugger worked. I can now set the refresh rate and resolution as if the monitor is directly connected to the computer. Here's how to do it:

Run regedit, and go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\DISPLAY\Default_Monitor

This section contains settings for monitors with no EDID info. There may be one or more monitors listed there, possibly depending on how much juggling you've already done. Mine had two. If you are connected to multiple monitors, you may need to figure out which is which. The rest applies to a single monitor case.

The monitor keys look like random strings with numbers, "&" symbols and letters in them. Open one of them and select "Device Parameters". That key should contain a binary value called BAD_EDID.

Right click "Device Parameters", and add a new key called EDID_OVERRIDE.

Select EDID_OVERRIDE, and add a binary value called 0 (plain zero, no quotes). If the EDID you will be copying there contains more than 128 bytes (80 hex), you may also need to add binary values 1 to 5. See the doc for more info. It talks about an INF file, but it all amounts to adding stuff to the registry.

Now you need a copy of the monitor EDID. I got mine by connecting the monitor directly without the KVM switch, in my case it added a section at

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\DISPLAY\GSM4A4D

The name will vary depending on the monitor brand and model. That section contains settings similar to Default_Monitor, except under "Device Parameters" there is a binary value called EDID filled with valid data. Double click EDID, and copy the first 128 bytes to the 0 binary value you added. If the EDID is longer, repeat for the rest of the 128 byte chunks and use values 1 to 5.

Repeat the procedure for all monitors at HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\DISPLAY\Default_Monitor, close regedit, reboot, and presto, the 60Hz lock should be history.

Emre, 

Thanks for the info.  I am using driver version 186.27 (latest Windows update driver without installing direct from nVidia) and it is doing what you want on my setup (I can turn my monitors off and on without any change to my desktop).  You may want to try the Windows update driver version.  I will try the latest nVidia drivers again to see if there is a change for me.

I have read and do understand this thread.  I think whatever the fix is, it should be a controllable fix.  My scenario is this: Projector is monitor 1 and external LCD is monitor 2.  I have my settings to "desktop only on 1".  Previously in Build 7100, whenever I turned off the projector, Windows 7 would treat the projector as disconnected and automatically move my desktop to the external LCD... quite seamlessly I might add.  Now I have to change settings prior to turning off my projector in order to keep using the computer.

I'm under the impression that each monitor should have a choice for how it is treated when disconnected.  Users of KVMs should be able to turn this "auto-desktop" feature off.  Users who want the ability to specifically turn off their monitor or have monitors that do not transmit EDID data in standby mode should also be able to turn the feature off.  Users who want their desktop to automatically resize should have the ability to use this auto-desktop "feature" (specifically laptop users).

Again, I want the problem you have and you want the problem I have.  Lets swap monitors.

-Chris

Emre, 

What nvidia driver version are you running?  The problem you have is the feature I want.

cray54, below you can find the System Information Report created by my NVIDIA Control Panel. You can see my GPU driver in bold. I should also remind you that this behaviour is really annoying me (and the rest of the users here) since it causes my windows to resize themselves on their own will when I turn off and turn on my monitor. And by the way, I guess that this strange issue is more likely to be caused by my monitor but noy my GPU/GPU driver. If you could read the previous posts on this thread, you can realize that my LG LCD monitor is probably not sending EDID data via DDC channel to Windows 7 continuously (stops sending it when it's turned off) causing Windows 7 to lower the screen resolution of the system to a safe or default level which wasn't the case on Windows Vista & Windows XP. We simply want to stop this service or whatever it is in Windows 7 so we can get this issue fixed.

NVIDIA System Information Report created on: 01/15/2010 18:52:00

System name: EMREEROKYAR-DT

[Display]

Processor: Intel(R) Pentium(R) D CPU 3.00GHz (3907 MHz)

Operating System: Windows 7 Ultimate, 32-bit

DirectX version: 11.0

GPU processor: GeForce 6800 GS

Driver version: **** 195.62

Core clock: 425 MHz

Memory clock: 1000 MHz (2000 MHz data rate)

Memory interface: 256-bit

Total available graphics memory: 1023 MB

Dedicated video memory: 256 MB

System video memory: 0 MB

Shared system memory: 767 MB

Video BIOS version: 5.41.02.49.04

IRQ: 16

Bus: PCI Express x16

[Components]

nvCplUI.exe 2.8.254.08 NVIDIA Control Panel

nvWSS.dll 6.14.11.9562 NVIDIA Workstation

Server

nvViTvS.dll 6.14.11.9562 NVIDIA Video Server

nvMoblS.dll 6.14.11.9562 NVIDIA Mobile Server

NVMCTRAY.DLL 8.17.11.9562 NVIDIA Media Center

Library

nvDispS.dll 6.14.11.9562 NVIDIA Display Server

NVCPL.DLL 8.17.11.9562 NVIDIA Compatible

Windows7 Display driver, Version 195.62

NVCUDA.DLL 8.17.11.9562 NVIDIA CUDA 3.0.1

Driver

nvGameS.dll 6.14.11.9562 NVIDIA 3D Settings

Emre, 

What nvidia driver version are you running?  The problem you have is the feature I want.

I have an LG W2261VP 22" LCD monitor. When I turn off my monitor by touching it's power button, Windows 7 plays the sound "Device Disconnected". When I touch back on the power button to turn my monitor on, Windows 7 plays the sound "Device Connected", just like I unplugged and plugged back the DVI cable to my GPU (GeForce 6800GS). And when I do this, I will have all my windows which are not maximized and minimized get resized and usually moved to an upper left side of the screen.