KVM w/ DVI-I and HDCP failure

Hi, I also have this problem, with exactly the same symptoms. I also think it is to do with hdcp because, if I plug my mini straight into my monitor (which is hdcp compatible), I don't have this problem.

So, I'm going to buy a new hdcp compatible kvm switch to replace my old Belkin non-compatible one. I will report back if you want me to. I should have the new switch by the beginning of next week.

Got my new KVM switch today (Aten CS1782). I have now connected it to my mini and can report that I have no more screen flickering problems as described in the OP. I assume then that the problem must have had something to do with the HDCP on the new Mac mini. My new switch is HDCP compliant - the old Belkin one was not.

Hopefully, there will be a firmware fix in the future for those who have this problem. Unfortunately, I could not wait, and needed the use of both my computers - PC & Mac - so bought the new switch.

Thanks for following up on this. I just bought my first Mac 3 days ago (a mini) and was struggling with video issues. I've been a PC user since 1985. Only one other time did I have these kind of video issues (trying to get 1920x1200 dual displays working on an IBM Thinkpad T42).

I spent a day trying to get 1920x1200 out of the Mini DisplayPort to VGA adapter for my Dell 2407 though the Dell 8-port VGA KVM (71PXP made by Avocent). I FINALLY got that working by downloading SwitchResX and adding a custom resolution/timing. Hopefully it will stick after removing SwitchResX.

Then, I hooked up the Mini DVI to DVI adapter to get my dual display. First, I had to go find another cable. Seems the adapter that Apple ships is DVI-D and not DVI-I. All my cables were DVI-I so I could go either direction (analog or digital). I got the new cable, hooked it up to my Avocent Switchview DVI, held my breath as I booted the mini and deflated when I saw snow, screen, snow, screen, snow, screen. Exactly the same thing as the OP. Nothing I did had any effect, so your findings are fortuitous. I have had zero issues with the Switchview until now. When I bought it, it was the only one that officially support 1920x1200. I now have the CS1784 on order.

Thanks for your due diligence. Hopefully my full explanation will help someone else who is googling for an answer. (Amazing how google has become a verb)

I notice Apple have just released a firmware update for people having issues with their mini-displayport to VGA adaptor. If enough people complained about the issue brought up by the OP in this thread, would Apple release a patch to fix this issue as well, I wonder?

Personally, I don't mind spending money on a new KVM switch, as the Aten is a lot better then my old Belkin switch. Finally, I can switch computers using a keyboard shortcut. I would definitely recommend the Aten to Mac users looking for a good, compatible, KVM switch.

Well, my Aten Master View CS1784 DVI KVMP (heh, p for usb ports?) just arrived. I hooked it up exacly as the Avocent Switchview 4SVDVI10 KVM was hooked up and everything is golden right out of the box. At the moment, it's only doing V out of KVMP since everything else is running through my 8 port Dell KVM (1 analog and 1 digital out of all my systems).

So, I can confirm what Paul found - the Aten CS1782/4 does not display the same flash/snow issues that exist on the Belkin or Avocent DVI KVMs. It looks like Avocent hasn't updated their firmware since 2007. I'll check in with their support and see if they have plans to fix this. Until they do, I would not recommend this Avocent switch for Mac users. I DO second Paul's recommendation for the Aten. It works fine accross my Intel i7 systems, IBM and Lenovo notebooks, and this new 2009 2GHz Mac mini (using the miniDVI to DVI adapter that ships with the mini).

Read this post after I made a long post the same as OP's above.
http://discussions.apple.com/thread.jspa?messageID=9426057&#9426057

I have a Rextron DVI/USB DAG12 switch.

I also noticed opening iTunes or Quicktime will bring the snow back and quitting it and replugging the cable a few times usually brings it back.

I also got a MiniDisplayPort to DVI DualLink as per a recommendation from AppleCare and it seems to work. On boot I get 5secs of the snow, it goes to the BLue screen then the desktop. Opening iTunes or Quicktime now doesn't take me back to snow. I do however sometimes on boot get a black screen with "Cannot Display This Video Mode" message. and it suggests the same resolution that I was already using. Unplugging the cable again fixes it.

I also noted a Philips 15" Screen at 1024 x 768 works fine. I will see if any HDCP DVI switches are available here & see how the price compares to Apple DualLink adaptor.

Matt

Well it seems Apple's DualLink adaptor also sometimes gives me the snow a few seconds after I switch back to my MacMini from my Dell, it however only lasts 4-5 seconds and goes away.

Paul or cedar do you think it is indeed the HDCP Complaint factor of the CD1782? or could it just be the newer DVI hardware/firmware in it?

i.e. the specs list "Superior video quality - 3840 x 2400 (DVI Single Link)*; 2048 x 1536; DDC2B (DVI-A)"

whereas older ones are usually something like "Superior video quality - up to 1920 x 1200; DDC2B"

Matt

Yep, maybe the HDCP thing might be a red herring? I just sold my Belkin and noticed it could only support 1600x1200 resolution. However it had no problem driving my previous Mac mini at 1920x1200 resolution.

I did phone Apple about the KVM Switch issue and got through to one of their Indian call-centers. They recommended taking my new Mac mini in for repair. As I didn't want to do this, and had a hunch it was my KVM, I thought I might as well buy a new KVM Switch. I mentioned HDCP to the tech, but they didn't know anything about this (this was when the new mini had just come out).

As most of the KVM Switches I considered were HDCP compliant, it was an easy decision to make anyway. And I haven't had any snow issues since. I'd still like to know whether it's an HDCP or a DVI hardware/firmware issue though?

The 9400 GPU the macmini uses is HDCP compliant so I'd be more likely to blame it on the KVM switch. If you read the support sites of some of the KVM makers they will specify that that certain switches are limited to certain resolutions using DVI.

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