MP 1,1-5,1 USB Connections Cause Screens to Not Work

ZombiePhysicist

macrumors 6502a
Original poster
May 22, 2014
706
461
So I have a weird problem. I have 6 30" Cinema displays hooked up to my 5,1 2010 Mac Pro. I'm currently using two 5770 cards to drive them, but have tried this with other cards and the same thing happens. Which is...

At some point my 6 displays stopped working and only 5 will show up. If I try to plug all 6 in the 6th will try to display, but will cause other displays to flick on and off and the desktop will move around between the screens trying to reconnect. If I unplug one, everything is fine. Now the 6 worked fine for YEARS and nothing really changed as far as I can tell. If I use my Amd w9100 card, samething happens. As does my 6 mini-display port 5870 card.

Here is the weirder thing. If I plug in any external USB device (thumb drive, external drive) it makes my 5 working displays do the flicker dance and won't work unless I unplug another screen and go down to 4 screens.

Soooo. Any ideas as to what the problem might be? I'm thinking it might be an old capacitor on the motherboard or power supply going? Has anyone seen anything like this before?
 

bookemdano

macrumors 65816
Jul 29, 2011
1,211
701
IIRC the 30" Cinema display is Dual-Link DVI, correct?

So are you using six of these: https://www.amazon.com/Apple-MB571Z-DisplayPort-Dual-Link-Adapter/dp/B001IF252C?

Have you considered that one or more of your adapters could be causing the problem? I've never used that adapter, but it looks like it's an active adapter, meaning it needs external power from a USB port. Have you tried plugging all of the adapters' USB connections into an external powered USB hub?
 

ZombiePhysicist

macrumors 6502a
Original poster
May 22, 2014
706
461
IIRC the 30" Cinema display is Dual-Link DVI, correct?

So are you using six of these: https://www.amazon.com/Apple-MB571Z-DisplayPort-Dual-Link-Adapter/dp/B001IF252C?

Have you considered that one or more of your adapters could be causing the problem? I've never used that adapter, but it looks like it's an active adapter, meaning it needs external power from a USB port. Have you tried plugging all of the adapters' USB connections into an external powered USB hub?
Thanks. Im using 4 of the apple adapters and 2 Dual link DVI cables with the two AMD 5770 cards (thats what they have for connectors). On the other cards I use 6 mini display ports with the adapters. Odd thing is with the 2 DVI ports on teh 5770 I can drive 5 monitors. If I use all mini display ports, I can only use 3 or 4 monitors. And yes, all the USB plugs are all plugged into a powered USB hub.

Again, it worked for years. Like 7 or 8 years and then like 2 years ago it just started to flake out. Super weird.
 

bsbeamer

macrumors 68020
Sep 19, 2012
2,402
1,116
Again, it worked for years. Like 7 or 8 years and then like 2 years ago it just started to flake out. Super weird.
What OS did you first notice this on? What OS are you on now? What BootROM version?

A problem from two years ago that you're troubleshooting now can be difficult to easily pinpoint. Suggest you try one monitor at a time with the adapters to see if any of them act up. Then "group" that monitor and adapter together and try another pair.

A client semi-recently had their 30" ACD finally crap out. I suspect it was a bad cable to the monitor itself (the umbilical cord) that would have been difficult and expensive to replace for the age and quality of the monitor. The PSU power adapter box also was getting extremely warm and would occasionally grey out the screen or cause almost a blowout/burn (reminiscent of plasma displays). Those PSUs can be cobbled together with non-Apple replacements for under $40 in parts if you're handy and search.
 

ZombiePhysicist

macrumors 6502a
Original poster
May 22, 2014
706
461
What OS did you first notice this on? What OS are you on now? What BootROM version?

A problem from two years ago that you're troubleshooting now can be difficult to easily pinpoint. Suggest you try one monitor at a time with the adapters to see if any of them act up. Then "group" that monitor and adapter together and try another pair.

A client semi-recently had their 30" ACD finally crap out. I suspect it was a bad cable to the monitor itself (the umbilical cord) that would have been difficult and expensive to replace for the age and quality of the monitor. The PSU power adapter box also was getting extremely warm and would occasionally grey out the screen or cause almost a blowout/burn (reminiscent of plasma displays). Those PSUs can be cobbled together with non-Apple replacements for under $40 in parts if you're handy and search.
Thanks, Yea, we're likely talking OS version 10.10 or there abouts. I have tried using each of the 6 monitors in groups of 3, and all 6 work, just not more than 4 or 5 at any one time. Meaning, I could disable any one of the 6, and then all other 5 work just fine for the work space.

It's a truly bizarre issue where interaction with USB will set off all the monitors to flick on/off unless I disconnect any one of them. Again, the only thing I can speculate is it has something to do with power, but it doesnt seem to have to do with PCI power draw. For example, having two 5770 cards or a single low power PCI card only with no additional power draw, the issue still persists. So my speculation is it has something to do with a capacitor serving USB channels and why and how that somehow interacts with the displays is just baffling, but in someway it must.

Thank you all for your speculations and suggestions, and please, keep them coming. I do appreciate it. Right now I think my course of action will be to get a new power supply and see if that helps, and then I would likely need a new motherboard, which I'm loathe/hesitant to do as I'll need to brain transplant the CPUs, updated wifi/bluetooth and other things that have been customized. I just want to avoid gutting the system if I don't have to, but it may come down to taking it to a service center and paying for new motherboard and power supply just to make sure the problem gets solved.
 

crjackson2134

macrumors 601
Mar 6, 2013
4,515
1,633
Charlotte, NC
I would likely need a new motherboard, which I'm loathe/hesitant to do as I'll need to brain transplant the CPUs, updated wifi/bluetooth and other things that have been customized. I just want to avoid gutting the system if I don't have to, but it may come down to taking it to a service center and paying for new motherboard and power supply just to make sure the problem gets solved.
Don’t let changing the Backplane Logicboard intimidate you. The 1st time I did this I took about 90 minutes. The next time took me 45 minutes.

Just read the relevant sections of the Tech Service manual, watch a video, and reach out here for help if needed. It’s quite easy, don’t psych yourself out.
 
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