Mac Mini display problems with KVM

Question

1994BF Author

Level 1

4 points

Mac Mini display problems with KVM

The Mac Mini and 23" display were purchased 3 years ago and have worked well together. The other items listed below have been purchased recently. I bought the the Flip to use the display, keyboard and mouse with both computers. The Powermac G4 has a video card with ADC and DVI connectors.

When the Flip is switched to the Powermac, everything is fine. When the Mac Mini is selected, the display goes bonkers. It starts slowly, with occasional horizontal lines flashing across the screen. It builds to where the screen is filled with flashing lines and dislocated images. The display also randomly blacks out for 1-2 seconds. Switching the Flip button back and forth restores order temporarily.

I have tried interchanging the Flip cables between the computers, but there is no change - the display problems stay with the Mac Mini.

The Flip uses dual link DVI while the display is single link. Is it possible there is a problem at the Mac Mini connection?

Mac Mini G4, Mac OS X (10.4.11), Powermac G4, 23" Cinema Display, Apple Aluminum Keyboard, Logitech USB Marble Mouse, Belkin Flip KVM

Posted on Aug 21, 2008 10:07 PM

Reply

Answer 1

Boece

Level 5

6,264 points

Aug 22, 2008 4:59 AM in response to 1994BF

Is this the model of Belkin Flip that you have?

http://catalog.belkin.com/IWCatProductPage.process?Product_Id=375076

Reply

Answer 2

1994BF Author

Level 1

4 points

Aug 22, 2008 11:17 AM in response to 1994BF

Boece,

Yes, model F1DG102D.

Reply

Answer 3

Boece

Level 5

6,264 points

Aug 22, 2008 11:32 AM in response to 1994BF

Do you know what display settings you have selected in System Preferences?

This was the troubleshooting help at the Belkin site:

Monitor Support

I am getting ghosting, shadowing, or fuzzy images on my monitor.

* Check that all video cables are inserted properly.
* Check that the monitor you are using supports the resolution and refresh-rate setting on your computer.
* Check that the graphics card you are using supports the resolution and refresh-rate setting on your computer.
* Connect the monitor directly into the computer with which you are having trouble with to see if the problem still appears.

Reply

Answer 4

1994BF Author

Level 1

4 points

Aug 22, 2008 4:55 PM in response to 1994BF

The display and Mac Mini have worked together fine for 3 years. The Mac Mini has an ATI Radeon 9200 video card. The Power Mac has a GeForce4 MX video card. Both cards have 32MB VRAM and 32-bit color. Both computers are set for 1920 x 1200 resolution.

Reply

Answer 5

Boece

Level 5

6,264 points

Aug 23, 2008 6:57 AM in response to 1994BF

Do you have any refresh options in System Preferences Monitors? For example can you use 60 Hz instead of 70 Hz?

(BTW does Monitors Sys Pref identify your monitor by name when going thru the KVM? If not, that may be the ultimate source of the trouble; the mini doesn't know who it is talking to.)

Reply

Answer 6

BSteely

Level 5

7,643 points

Aug 23, 2008 7:19 AM in response to 1994BF

The Mac mini is touchy about something known as coherency with respect to digital video devices it attaches to. You can see the reference to this under the "Video" heading in the below document:

http://support.apple.com/specs/macmini/Macminiorig.html

It would appear that the Flip's DVI receiver is having trouble with the mini at the high pixel clock rate required to drive 1920 x 1200. If I were you I would contact Belkin about this and see what they have to say. It could be that a replacement Flip would work better. EIther that or you might need to return it for a different brand KVM.

Reply

Answer 7

1994BF Author

Level 1

4 points

Aug 23, 2008 11:31 AM in response to 1994BF

The mini does not offer refresh rate options.

In System Profiler, the mini identifies the display as Cinema HD Display; the Power Mac identifies the display as LCD.

The Flip handles the pixel clock rate properly for the Power Mac (MDD dual 867MHz PPC G4), why would it not handle the mini (1.42 GHz PPC G4) as well?

Could it be the mini's graphics card (ATI Radeon 9200) can't drive the display properly thru the added cable and hardware?

Reply

Answer 8

BSteely

Level 5

7,643 points

Aug 23, 2008 10:10 PM in response to 1994BF

+"Could it be the mini's graphics card (ATI Radeon 9200) can't drive the display properly thru the added cable and hardware?"+

In a sense, yes, that is likely what is happening. The TMDS receiver within the Flip may be of the non-coherent type and the mini can't drive it, even though the MDD can.

Reply

Answer 9

1994BF Author

Level 1

4 points

Aug 25, 2008 2:22 PM in response to 1994BF

According to Belkin telephone support, the F1DG102D suppports coherent and noncoherent displays. The Cinema HD Display is a coherent display.

Reply

Answer 10

BSteely

Level 5

7,643 points

Aug 25, 2008 8:24 PM in response to 1994BF

Then I would ask Belkin for a warranty replacement. If the mini drives the Cinema directly without trouble, and inserting the Belkin in-line causes trouble, then it seems you got a deffective or marginal Flip.

Reply

Answer 11

1994BF Author

Level 1

4 points

Aug 27, 2008 3:07 PM in response to 1994BF

Belkin support e-mailed me today and suggested I reset the Flip by disconnecting and reconnecting the flip cables from both computers while they were on.

This has helped the situation immensely, but random lines still flash across the screen occasionally.

I will try another reset later.

If that doesn't totally clear up the problem, Belkin requested I exchange the Flip for a new one.

I will follow up with a post next week.

Reply

Answer 12

1994BF Author

Level 1

4 points

Sep 2, 2008 5:43 PM in response to 1994BF

After resetting the Flip a couple of times, the original problem remains. However, at times the screen will be perfectly stable for up to 15 minutes before reverting to its evil self.

I will be returning the Flip for a new one.

After connecting the new Flip I, will post my results.

Reply

Answer 13

1994BF Author

Level 1

4 points

Sep 10, 2008 3:14 AM in response to 1994BF

Belkin sent a replacement kvm and after trying it, I sent it back. The display, when switched to the Mac mini, was more unstable with the replacement kvm than with the original kvm. When switched to the Power Mac G4, both kvms acted properly.

Since it is now too late to return the original kvm to the store I bought it from, I'll live with it until I can afford to try a different brand. That's what I get for ignoring the advice to buy kvm's from stores with liberal return policies.

I am also going to ask Belkin if they tested this model kvm with the Mac mini.

Reply

Answer 14

Boece

Level 5

6,264 points

Sep 10, 2008 5:40 AM in response to 1994BF

+the advice to buy kvm's from stores with liberal return policies+

Good advice, indeed!

Reply