New Mac Pro, Multiple displays not all coming on at startup

This writing is not a defense of the current problems of multiple displays not becoming active at Startup. To get action on that item, you will need to make Apple aware that you consider it a problem, such as by calling telephone support.

The Mac uses a single, highly-paramerterized driver for every display. The parameters for the driver are set and reset in response to the display's answer to the EDID query sent at certain times. If the query is not answered for any reason, the display will not be illuminated.

The times when the query is sent are:

1) at Startup

2) at cable insertion at the Mac-end

3) at wake from sleep

4) at invocation of the Option- ( Detect Displays ) button is the Displays Control Panel

I recommend that after you finish telling Apple how unhappy you are with with this bug, you try 'sleep and wake your Mac' to detect the rest of the displays.

in direct contradiction to the Apple Human Interface guidelines, you must hold down the Option key to see that button.

Some displays, especially multi-input HDMI displays, do not always 'pay attention' when the Mac sends its query -- especially if they are set to a different port (or automatically set themselves to a different port at power-on).

Your current issues with multiple monitors is not a new one. I too have the all most same setup as you except, I have (3) duel link active display adapters attached to the TB display ports and the use of the HDMI direct to monitor, with the same results. Prior to updating to Yosemite, Maverick with the same hardware operated without any issues. Once Yosemite was downloaded (10.10.1) the problems started. Apple had no resolve to this issue. However, its been rumored Yosemite's requirements upon the GPU (500 or 700) cards pushes these to the limit. There are threads on this issue with the pro community while editing with 4K monitors. You did not mention the type of card (500 or 700)?

The only resolve is to boot your system, and what ever monitor does not startup, unplug the TB or USB connector and replug same, this will startup the monitor.

This is really a problem.

Yes it is! With the Mac Pro 2013 running Mavericks, I had no issues with the displays. In fact, simply removing Maverick and replacing with Yosemite all the issues displayed their compatibility problems. It is rumored the 500 cards were pushed beyond their stats under Yosemite. There maybe a resolve to this, with replacing the 500 cards with the 700's, It seems there is less problems, yet some have indicated similar poor results under Yosemite.

It would be of interest to know when the Mac Pro 2015 will be out, this will have a different CPU.

Same issues, nothing works reliably. Unplugging not a good idea as at some point you will compromise the integrity of the connector ports. My best workaround is to use USB hubs with an on off switches and Monitors with an on/off switch. For startup, turn off the hubs, and see if all monitors turn on. If not, recycle either monitor using the on/off monitor button. Works every time without wear and tear on the connect ports on the MacPro. This is at best an inelegant solution but at least the ports won't wear down.

My 2 month old late 2013 Mac Pro started to show the problem since last week with Yosemite 10.10.3, and it got worse by waking up not even one display on. ( I have 6 monitors, one TB, 4 display port, one displayLink USB), initially I didn't realize the Mac woke up already so I have to hard reset every time, later on I found the Mac Pro was reachable thru other local computer as the share function is on, I can even SSH to it, the only problem is no display is waken. Only work around under yosemite is to reboot, but with 50% chance success, in fact I have to boot multiple times too to get all monitors up, I'm surprised this is not thoroughly tested in apple, why should people buy a 6 TB pro without apple even testing connect 6 monitors? So frustrated that I can't even use sleep, tried all kinds of setup in pmset with no effect, it woke up randomly sometimes reboot with a error message, sometimes mac just on but no display on like I mentioned. Searched high and low and found there's a lot issue with the sleep/wake problem, on all mac platform! Seems such a fundamental function works like a crap in Mac, worse than PC!

Surprised I didn't find many wake/sleep issues on Mac Pro from the community, but anyway I rolled back to Maverick and so far so good, at least I can put the Mac to sleep now, I can't confirm 100% it will be working as it's only been a few days since I downgrade. Hope it helps anyone who's frustrated with the issue.

10.10.4 available today, 30 June 2105, supposedly with fixes for display problems.

Just tried and same old problem, waking up on its own with no display signal. Downgrade to 10.10.2 now. The issue started on 10.10.3.

Re: Yosemite 10.10.3 Second screen big problem

My tremendous thanks for posting your issue here. I've been having the same trouble on and off for months now. Each time Apple's support team tells me they are stumped and escalates the issue to their "engineers". Never to be heard from again.

The culprit seems to be these two files on my system:

com.google.keystone.agent.plist

com.google.keystone.daemon.plist

They were removed from:

/Library/LaunchAgents

/Library/LaunchDaemons

I also removed a couple CleanMyMac folders as well, but I'm unsure if these had anything to do with that.

Both monitors I have connected are both working now.