2011 Mini DVI - HDCP issues with Matrix KVM?

[Robertsmania]

I had been using a 2009 Mac Mini which worked fine with my studio setup - it includes an older Gefen 4x4 DVI Matrix KVM switch.

Yesterday I got a new 2011 Mac Mini and am having problems with the colored static (snowstorm?) showing up every few seconds on some of the displays in the system.

Not every display shows the problem, and its weird because the ones that do are a monitor and projector which are both HDCP compliant. Monitors which do not support HDCP seem to work okay.

I have tried using both the supplied HDMI-DVI cable as well as a mini displayport-DVI adapter. Both show the same problem.

I have found some support threads about what I think must be the same issue that indicate it has to do with how the Mac decides to use HDCP or not - but I have not been able to find a reliable startup sequence or anything that lets me use all the displays with the new mini.

Has anyone else experienced issues like this with KVMs or DVI switches? Any work arounds or suggestions?

 

[Robertsmania]

I've done some more experiments and am confused because the problem happens with the displays that are actually HDCP compliant.

My displays are two Dell 2405FPW monitors, one Dell 2408WFP monitor and an Epson 8350 projector. The projector and the 2408WFP are HDCP compliant, but the 2405FPWs are not.

If I have the switch set to have either the 2408WFP or the Projector as the connected display for the Mac Mini when it boots up, it does get their EDID properly but the screen flashes to terrible multicolor static every few seconds.

If I switch it to display just on either of the 2405's, the static stops and the display works fine. It also works fine if I reboot with either of those as the connected display - it gets their EDID and works fine.

Once it is stable, I find that I can activate the 2408 and/or the projector and it will remain stable - until I switch away the 2405, then it starts with the static again.

 

[Robertsmania]

I think the problem must be with the integrated Intel graphics chipset and/or driver. Here is the bug report I submitted to Apple:

Summary:

The 2011 Mac mini with Intel HD Graphics 3000 and the 2012 Macbook Air with Intel HD Graphics 4000 do not work properly with a Gefen 4x4 DVI Matrix Swtich. When the switch is set to use a display that supports HDCP, the mini/air boots up fine and has a stable image up until the login screen. From that point on the screen is filled with multicolor static every few seconds. If the switch is set to use a display that does not support HDCP, the mini/air boots up fine and the image remains stable through the login screen and into use.


Steps to Reproduce:
Connect a 2011 Mac mini with Intel HD Graphics 3000 to a Gefen 4x4 DVI Matrix Switch.
Connect a HDCP compliant display to the switch such as a DELL 2408WFP.
Connect a non HDCP compliant display to the switch such as a DELL 2405FPW.
Power on the DVI switch and set it so that the mini is to use the 2408WFP display.
Power on the mini and observe that after the initial boot screens display properly that the screen starts to flash to multicolored static every few seconds once the login screen is reached.
Login and open the Displays System Preferences panel, confirm that DELL 2408WFP is shown in the top of the panel.

Power down the mini.
Set the DVI switch so that the mini is to use the 2405FPW display.
Power on the mini and observe that the display remains solid up until and after the login screen has been reached - the multicolored static is never seen in this configuration.
Login and open the Displays System Preferences panel, confirm that DELL 2405FPW is shown in the top of the panel.

Expected Results:
The display should be solid with either display.

Actual Results:
The HDCP compliant display is not usable due to constant multicolored static which flashes on the screen every few seconds.

Regression:
Check with other Mac computers which do not use the Intel HD Graphics 3000 or 4000.

The systems we have available to test are a 2007 Mac mini, a 2009 Mac mini and a 2012 Macbook Pro with Retina display. All three of those systems work properly with all the displays connected to the DVI switch using the same mini displayport to DVI adapter.

We have also checked with a PC system running Windows 7 using an Nvidia 680 graphics card and confirmed with the Nvidia Control Panel's View HDCP Status function that the switch and monitors are working properly and accurately reporting the expected HDCP status - namely that the switch passes the EDID values for the monitors correctly and that the 2408 shows a HDCP-capable link while the 2405 does not.


Notes:
We purchsed the new 2011 Mac mini to replace the older 2007 Mac mini in our studio, but the current issues using it with the DVI switch make it unusable. From searches looking for resolutions others have found to the same problem, we do not believe that the specific computers we have are defective but rather there are issues with the integrated Intel HD Graphics 3000/4000 drivers.