MacMini DVI colored static and KVM's

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Level 1

25 points

MacMini DVI colored static and KVM's

Hi

I manage 50 odd Mac's at work and have a new 09 MacMini. I have it connected via the Mini-DVI to DVI connector to a Rextron DAG12 DVI-I / USB KVM switch. I have been using the KVM for a year or 2 with a PowerMac G4 machine with no problems. When I connect the MacMini all I get is multicoloured static / a snowstorm (as described elsewhere) for about 3 seconds, then I see the actual screen for about 1 second and this repeats over and over making it unusable. I tried various resolutions / refresh rates and it made no difference. If I unplug and re-plug the DVI adaptor about 5 times it eventually stops doing this and I just get the screen as it should be. I then used it all day, switching between my mac and PC and left it on over the weekend and it was fine on Monday.

I discovered restarting the machine brings me back to the static mess (after the grey apple screens). As does opening iTunes or Quicktime. It appears to be related to video rendering. I also tested it on a new MacBook with the 9400 Nvidia chipset and get the static. I tried another 09 Mini and same problem. Tried another Mini-DVI adaptor and same problem. Tried both DVI-I and DVI-D cables from the switch to Mac.

I tried an older MacBook with the Intel X3100(?) chipset with the same DVI adaptor and it works fine. As did an old 1.83Ghz Intel based graphics MacMini.

Using the screen without the KVM seems to work OK but is no use to me. The fact that I can get it working for days as long as I dont restart or open iTunes / Quicktime seems to suggest it's something driver / software related to the Nvidia 9400 chipset on the Mac. Any ideas / thoughts? HDCP? I will try and get a mini-displayport to dvi connector to test that.

Matt

Message was edited by: Matt Hall

Macs o Plenty, Mac OS X (10.5.6), IT Technician, ACDT, ACHDS

Posted on May 5, 2009 4:08 AM

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Answer 1

Matt Hall Author

Level 1

25 points

May 5, 2009 10:11 PM in response to Matt Hall

Same results with a MiniDisplayPort to DVI adaptor. Anyone have a MacMini 09 model working via a different branded KVM? Belkin etc...?

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Answer 2

May 6, 2009 7:56 AM in response to Matt Hall

Matt,

It's been quite a while since I had this problem, so I was looking for my notes on fixing it. No luck there.

The bottom line is that the "native" refresh rate on your KVM is far enough out of specs for your monitor that it's affecting the display. When you plug directly into the mini, the display automatically senses the correct refresh rate and looks fine.

It's a hack, but here's what I did (after giving up on manually modifying the settings in Terminal and failing miserably):
1. Plugged the display directly into the mini and created a "calibrated" color profile for it in both user and admin accounts.
2. Connected the KVM and booted in safe mode, selected the "calibrated" color profile with appropriate resolution in all profiles.
2b. Made sure I unchecked the +Show profiles for this display only+ box in the Display > Colors tab for all users.
3. Plugged in the KVM and restarted in safe mode, doing 1 & 2 above.
4. Restarted and manually set the color profile and resolution.
It can take a few tries to get the settings to "stick."

-Wayne

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Answer 3

ceder

Level 1

0 points

May 6, 2009 3:21 PM in response to Matt Hall

I have had the same problem since I got my new mini. It's very annoying. On the thread I started earlier someone posted the model of a newer KVM with DVI-I that worked. It was not the cheapest, ~$400. But, it worked and can be ordered online.

When you finally get the display to stop being snow, you can make it start again by simply launching iTunes!!! Such convenience. Also, under Displays-> Detect Displays will start it snowing again.

I really hope this gets fixed by apple somehow. I develop on multiple OS's and use a KVM daily.

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Answer 4

Matt Hall Author

Level 1

25 points

May 6, 2009 4:56 PM in response to ParentalUnit

Thanks Wayne

I'm not sure this is the same problem though. What KVM do you have?

I get this static mess even when booting in Safe Mode or when booting from the Install DVD. I have been trying a MiniDisplayPort to DVI DualLink adaptor and it seems to fix some of the problem. On boot I get 5 seconds of static then it goes to a blue screen then the Desktop. Opening iTunes / Quicktime now doesn't take me back to Static. However sometimes when restarting I get "Cannot Display This Video Mode" Optimum 1280x1024 60Hz, which is what it was set to.... Unpluggin the miniDisplayPort cable and replugging brings it back.

I am trying some different settings with SwitchResX now to see if that makes any difference.

I will also try some other LCD monitors, 15" Philips and 22" widescreen philips.

Matt

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Answer 5

Matt Hall Author

Level 1

25 points

May 6, 2009 5:36 PM in response to Matt Hall

a 15" Philips at 1024x768 doesn't give me the Static & works fine. A Philips 20" Widescreen at any resolution is giving me static....

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Answer 6

May 7, 2009 4:28 PM in response to Matt Hall

Matt,

It's likely that this problem is specific to your widescreen monitor and your KVM, then. It still sounds like you're having a refresh rate mismatch with your KVM, since the monitor works correctly when you plug it directly into the Mac.
If my hack didn't work, I see two possible solutions: a. Different monitor. or b. Different KVM.

-Wayne

Message was edited by: ParentalUnit
Sorry I can't be of more help.

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Answer 7

Matt Hall Author

Level 1

25 points

May 10, 2009 8:59 PM in response to ParentalUnit

Thanks Wayne

I found this post also - http://discussions.apple.com/thread.jspa?messageID=9164619&#9164619 with the same issue. The iTunes / Quicktime opening factor also suggests perhaps something todo with HDCP. I have been through the AppleCare channel and they are passing it onto Engineering for investigation.

Perhaps it is some mismatch but in the Displays tab it shows as 1280x1024 @ 60Hz. I tried some custom tweaking with ScreenResX and had no luck there. Nor can I see why iTunes / Quicktime would be adjusting the resolution.

I am going to try and get a HDCP complaint KVM to test in the meantime.

Matt

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Answer 8

Matt Hall Author

Level 1

25 points

Jun 30, 2009 6:29 PM in response to Matt Hall

I have a partial solution for this. (That doesn't include buying a HDCP complaint KVM) E-Mail me ...

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Answer 9

Jul 14, 2009 6:07 AM in response to Matt Hall

Matt, I am interested in your 'partial solution' but I do not see a way to email you.

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Answer 10

Jul 15, 2009 2:20 AM in response to Matt Hall

I'm using an old iogear kvm switch with a 24" acer x243w lcd with my new mac mini 2009 just fine with no problems at all. I just had to shell out $30 for a displayport to vga adapter since the kvm switch is vga and not dvi though. Image quality @1920x1200 is indistinguishable from when using dvi so I'm happy 🙂
Did have to hit detect displays to get 1920x1200 resolution to show up on mini at first though otherwise will only do 1600x1200.
http://discussions.apple.com/message.jspa?messageID=9731813#9731813

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Answer 11

Matt Hall Author

Level 1

25 points

Sep 28, 2009 4:37 PM in response to GizmosTail

Yeah sorry it appears you can't e-mail me via this. e-mail me at mattosaur4@gmail.com

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