FileVault, El Capitan, 4K Monitor and Late 2013 Mac Pro

I haven't updated to Sierra because I'd lose compatibility with my version of LightWave. I'm saddened to hear it's still the same.

Regardless, I'm still stuck with it in El Capitan—and I found out that there IS a limit to how many blind login attempts you can make. My entire machine was bricked and I had to use iCloud recovery to unlock it. Thankfully that worked, but super stressful.

My main workaround is to never power down anymore (sleep/wake has the same problem, but less often). Not much of an answer when I need to travel.

(As for turning off FileVault: the owner of this building and dozens of employees have access to the master key. My clients' info is on the machine, not just my own. Turning off encryption and "taking my chances" would be irresponsible—not to mention a stressful and lengthy process to wait through.)

I have a variant of this problem.

Asus PQ321 running 4K@60Hz via MST DisplayPort on MacPro with D700s.

Filevault enabled.

Any reboot - blank screen.

IF I connect via HDMI only gets 4K@30Hz but does boot up.

Once I boot I can swap back to DisplayPort and up comes 4K@60Hz.

The ritual now is anytime I need to reboot, I connect via HDMI until booted.

Painful yes, but it works.

Hopefully you do not have this issue anymore, however I found a fix for this:

- Disable FileVault if you can. This will solve the issue of the monitors not working on the login screen. If you cannot, follow these steps, you need to plug in a working monitor to show the login page, or plug in an HDMI cable to your computer and monitor (if your monitor has an HDMI port) so you can see which direction your user account is.

Now, restart your PC once you have a working monitor in place. Once you see the login page, press the left or right directional arrows on your keyboard (you must plug in your keyboard to your Mac, not thru the monitor for this to work) and record how many times you press the left or right arrow keys to select your account at the login page. Press enter, and your password box should pop up to let you type in your password. Once you've figured out how many strokes and which direction to push the arrow keys. Plug back in your non-working monitor(s) and follow these steps:

1. Start your computer normally and wait about 15-20 seconds. The screen(s) should still be completely blank.

2. Press the corresponding number of left or right directional keys and press enter to type in your password.

3. Enter password and press enter.

4. Wait around 15-30+ seconds for Mac OS to boot up. Once you reach your desktop, the displays should load up and you'll be able to see your screen(s).

This worked for me, and it is a work-around unfortunately if you have to have FileVault enabled.

Try updating to 10.11.3

There are relatively few things that would make your Mac Pro power off. But one of them is not being able to mount the Boot Drive.

With the screen off, You may not be seeing the evidence of this happening.

Have you disconnected everything except the 4K monitor?

ist this problem solved? I have exact the same problem too

It won't startup with a 4k monitor attached via thunderbolt if filevault is enabled.

This is a problem I've had open with engineering for some time. This has been an issue for multiple releases of the O/S and is an issue across multiple resolutions and monitor manufacturers.

If you connect a non-4k monitor to the thunderbolt port then it works fine. I've also had it work properly with an Asus PQ321Q (UHD).

It fails for me with both the Dell P2715Q (UHD monitor) and the LG 31MU97 (4k monitor).

If you boot with a non-4k monitor and then connect the 4k monitor you can then disconnect the non-4k monitor; but the non-4k monitor has to be connected for each time you reboot or startup.

If you boot up with a non-4k monitor and turn off filevault you can swap a 4k monitor for the non-4k monitor during reboot and it will start up fine.

This is extremely frustrating.

My Mac Pro is JUST out of warranty. Same issue 😟 (My post is here.)

But for me, I have no video out to ANY device, including my simple 1280x800 HDMI projector, even after forcing multiple reboots with my 4K (Dell) display not connected at all.

So I think it's a Mac Pro/GPU issue in general, affecting some displays and not others (?), but NOT an issue specific to 4k displays.

Two other symptoms of this situation: caps-lock key won't light (Apple BT), and volume keys don't click. AFTER logging in, video works, and caps-lock and volume behave normally.

In case it hels you: the only way I'm surviving is that I discovered by trial and error that the machine isn't quite a total brick. You CAN log in. Then the video appears.

Here's my ritual:

1. Cold boot the machine. If it's already on, force-shutdown (hold power button until machine goes dead).

2. Wait... an arbitrary amount of time for booting. Haven't figured out the optimal timing. Too soon and you can't log in. Too late and the machine sleeps, but you can wake it with the power button (in fact, this re-weaking may make the display come on—but it takes so long to happen that I don't use this method).

3. Hit Esc a few times to clear anything that may pop up. What? I cannot say. Bluetooth wizards? I just know that sometimes logging in doesn't work, so I do this preventively.

4. Move the mouse (blindly) to top-left and click, to make the login screen "active." (Sometimes it isn't—I've long noticed that even when I used to have video.)

5. Type enough of your login name (even one character) to be unique, and press Return.

6. Carefully type your password and press Return. (Be careful not to touch Caps Lock. I think the key does work, it just doesn't light up, so you don't know it.)

7. Hold your breath and wait.

8. If nothing shows up after a while, try unplugging/replugging power to the display.

9. If that fails, repeat from step 3. (I really hope there's no limit to Mac login attempts.)

10. If THAT fails (and sometimes it does!) force-shutdown again and repeat from step 1.

This is all VERY stressful, including the ugly force-shutdowns, but so far, I have been able to get my Mac running after a power-down. Knock on wood.

Other blind experiments I want to try to make video appear: VNC screen sharing (maybe to iTeleport on my iPad), Safe Boot with Shift, booting with Option key (to choose startup disk), booting to recovery mode, and logging in as Guest so there's no password to get wrong. (But with File Vault, I know Guest mode takes extra steps/reboots.)

This is a horrible problem, and I do not mean to make light of it.

But why not turn OFF FileVault for your desktop Mac Pro for the time being until this problem gets cleared up. Enable findMyMac for use in the unlikely case that its gets stolen -- then you can track it and remote-lock it if needed. And disable auto-Login to slow down anyone who grabs it.

These are not nearly as stealable as a MacBook, and if you are working where it will be subject to theft, get a lock and/or bolt it to the table.

Still not fixed. Unbelievable.