KVM switch + Windows 7 creates monitor switching nightmare

Hi Trees,

I wonder if your problem could be related to this:

http://www.ddwg.org/lib/Dual_EDID_guide10.pdf

Apparently the EDIDs for the digital and analog part of a DVI interface may be different, but they are polled through the same DDC pins. If the monitor is connected with a DVI-I cable the computer side may not know which one it is getting. They suggest using a DVI-D or a DVI-A cable as a workaround.

In your case the HDMI-DVI connection should work, since there's no analog part involved. Changing the other one to use the VGA would force that one to use analog and might fix it, or use a DVI-I to DVI-D dongle if there is one, or if you are adventurous just snap off the analog pins from the connector. The pinouts are here:

http://www.interfacebus.com/Design_Connector_Digital_Visual_Interface_DVI_Bus.html

Commentary here and my experience reflects a problem with communication between windows 7 and drivers.

In my case with a HDMI (in use), DVI (in use) and VGA port off a Gigabyte GTX275 Windows 7 gets inconsistant results varying from 1 to 4 identified displays mapped to any combination of (including phantom duplicates)

• Dell 24 (Digital)
• SyncMaster (doesnt specify digital --- what does that mean?)
• Generic non PnP

Right now the combinations are

1 - Dell (screen pictue in Control Panel accurately reflects active and 1920x1200 res.)

2 - Syncmaster (screen pictue in Control Panel accurately reflects active and 1600x1200 res.)

3 - Generic non PnP (screen picture in Control Panel in is grey and small)

4 - Syncmaster (screen picture in Control Panel is grey and small)

the dell 24 lcd is currently plugged to HDMI (DVI Cable, HDMI-DVI adapter)

the samsung 214T lcd is currently plugged to DVI (DVI cable)

the VGA port isnt used (hmm... i might just put this to some use and see what happens next)

Hi 12 Stringer,

If there is no "Default_Monitor" section in the registry, you shouldn't add one yourself. The existence of that section is an indication Windows was not able to get the EDID from the monitor, and if that section is missing the problem is somewhere else.

In your case it sounds like for some reason the internal monitor keeps waking up every now and then by itself, and if the monitors use clone mode that would force Windows to make the resolutions match. Using extended mode as a workaround might help.

For the ones that have a problem with just a single monitor, assuming you don't have Default_Monitor section in the registry either, the problem could be W7 not getting the same EDID from the monitor every time. Assuming W7 always assumes the EDID it gets is valid, and if the EDID polling sometimes stops halfway for some reason, it could then make Windows think the monitor keeps changing, because the capabilities it reports back change.

If that is the case a workaround could be using EDID override to override all EDIDs in the registry with a good copy, but knowing what to replace with what could be tricky. And it may not really fix the whole problem, because if the EDID polling really is erratic, who knows how many different bad copies end up getting added to the registry.

Sheesh, what will it take to get Microsoft to fix this?  I "upgraded" from Vista Ultimate 64-bit to Windows 7 Ultimate 64-bit, and now my monitor keeps going offline (black) and back online at random times.  It worked fine before.

Microsoft, please enable us to choose the old behavior.  This flaky behavior is totally unacceptable and incredibly frustrating!  Hard to believe that Windows 7 could actually be worse than Vista, but that's how it feels!

My setup is this: I keep my notebook lid closed and have an external keyboard, screen and mouse attached through a KVM to this system and to one other one.  The external 1280x1024 monitor is "Display 2" and I have Windows set to "Show desktop only on 2".  Based on how my windows are getting moved around while the external monitor goes black, it appears to be randomly switching from the external monitor to the internal and back again, or at least switching to the internal resolution (1600x900).

I tried putting an EDID_OVERRIDE under "Default_Monitor" (which I had to add) and under "SAM034D", but neither helped.  Specifically, I added binary data "0" under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\DISPLAY\SAM034D\5&63d2442&0&UID257\Device Parameters\EDID_OVERRIDE and under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\DISPLAY\Default_Monitor\5&63d2442&0&UID257\Device Parameters\EDID_OVERRIDE.  I copied it from binary data "EDID" under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\DISPLAY\SAM034D\5&63d2442&0&UID257\Device Parameters.

If I misunderstood how to set up EDID_OVERRIDE, please correct me.  Thanks.

I have this problem on multiple monitors and it is not related to KVM.  The first and main monitor is a HP LP3065 30 inch 2560x1600.  The analog monitor is a 13 inch Asiatic rim 1360x768 that is on a VGA extension cable away from the main setup just above equipment where a few tasks need to be done with a wireless keyboard.  That monitor was picked to fit in a smallish space that is not subject to reorganization without some construction expense.  Every time the system reboots for any reason, W7 assigns the analog monitor as primary, assigns it an incorrect size of 1024x768, and blanks the HP3065.  If I power cycle the HP, the HP comes back on, but only displaying the 1024x768. W7 has reassigned the analog as monitor 1.  All the icons have been moved to the analog monitor and the HP is 1024x768 stretched out to 2560x1600. 

The HP3065 is correctly identified by W7.  It identifies the analog as generic pnp. If I bring up all the definition windows, I can force the HP3065 back to monitor 1, redefine both of them to their correct sizes.  It cost me a day to figure out this completely unsatisfactory workaround.  More time to find this thread.  I need to be able to *FORCE* the HP as monitor 1, *FORCE* the HP to 2560x1600 and *FORCE* the analog to 1360x768, and *FORCE* W7 to leave those settings alone, *REGARDLESS* if it sees a monitor off or not.  People turn off monitors to conserve power.  We get power hits that blink the monitors but not the PC which is on the UPS.

This is a really ugly bug to foist on us AFTER the release candidate.

The upgrade to W7 is taking on sinister aspects with this.  Are we going to get taken off line every time that MS decides to update a copyright scheme so that Time-Warner and Sony can feel all comfy when they go to bed at night falsely thinking that the latest genius teenage hacker has been defeated? I really don't want to bear the brunt of their copyright problems.