[Help!] Mac Pro 5,1 with GTX 680 and LED Cinema Display black screen

[VelNZ]

Hey all,

I've got a Leadtek GTX 680 4GB (bought off eBay) in my Mac Pro 5,1 that I've been using to power 2x 23" Apple Cinema Displays (the older aluminum ones). One plugs into the DVI port of the graphics card and the other goes through a DVI->HDMI adapter into the graphics card, no issues here, works great. The only other port on the graphics card is a Displayport.

After Apple's departure from the display business (oh god why), I decided to upgrade to the last displays that will work with my Mac Pro: the 27" LED Cinema Displays (Mini Displayport). I bought one and it works great with my 2013 Macbook Air through the Thunderbolt port so I know the display works. I then purchased a Mini Displayport (F) -> Displayport (M) adaptor (this one: https://www.amazon.com/StarTech-com-DP2MDPMF6IN-DisplayPort-Video-Adapter/dp/B003N3DTKY) but when I plug the display into the graphics card using it nothing happens. Rebooting does nothing, switching to the OS X display driver from the web driver does nothing. I have no idea how to fix it!

I've also tried connecting the monitor as so: Graphics card HDMI (F) <- HDMI cable (M/M) <- Displayport (M) to HDMI (F) adaptor <- Displayport (F) to Displayport (F) adaptor <- Mini Displayport (F) to Displayport adaptor (M)<- Cinema display 27" Mini Displayport cable (M). This also doesn't work even though it's using the HDMI port of the graphics card which works.

Any ideas?

 

[-VoiceOfReason-]

Are you sure it's a Mini DisplayPort Cinema Display and not the Thunderbolt one?

 

[VelNZ]

Are you sure it's a Mini DisplayPort Cinema Display and not the Thunderbolt one?

Yeah, it has 3 USB ports on the back and a USB 2.0 plug with Magsafe1 and Mini Displayport.

 

[h9826790]

Yeah, it has 3 USB ports on the back and a USB 2.0 plug with Magsafe1 and Mini Displayport.

The Thunderbolt Display's cables, port, whatever.... looks identical to the Cinema Display. However, the monitor itself won't work with any display port, it only works with the Thunderbolt port on a Mac. That means the cMP has no way to drive it, no matter which GPU / adaptor you have. (If you wrongly buy the Thunderbolt Display as the Cinema Display)

Update 1: I made a mistake, the Thunderbolt Display has firewire port which the Cinema Display doesn't have. So, it's actually easy to tell if it's a Cinema Display by checking the ports at the back.

 

[bax2003]

If monitor has just 3 port usb hub and usb at the compuer side it is 100% LED Cinema Display.

 

[Oorha]

Was this problem ever resolved, having the EXACT same issue.
Apple Cinema Display MDP to DP Geforce GTX 680, no screen detected ):

 

[VelNZ]

Nope, I ended up selling the 680 and buying an ATI card that works (Radeon RX560 4GB). It works great with both cinema displays.

 

[ActionableMango]

having the EXACT same issue.

A couple of possibilities.

1) Certain combinations of 680 and ROM resulted in one or more ports not working. EVGA cards generally worked. Most of the problems seemed to be with Zotac, exotic models, or oddball brand cards.

2) Most MDP to DP cables are not VESA compliant because they pass through pin 20 and should not be. The StarTech cable like OP had is known to be non-VESA compliant. Just search for the word "VESA" in the Amazon reviews for that cable and you will see.

Non-compliant cables can work in most situations, but not all. Hardware manufacturers caught on to the fact that most cables are non-compliant, so the problem mostly exists in hardware prior to or around the 2013ish era.

You can either try a known VESA-compliant cable like this Accell cable, or you can try to disable pin 20 on your existing cable by covering that pin with a very thin strip of electrical tape, taking care not to cover adjacent pin 18. Pin 20 is the one closest to the angled corner of the DP connector: