I have the same setup, except 6core. I am also doing the same work around. Does your console message say WindowServer: GPU Driver appears to be hung (over 5 continuous seconds of unreadiness) x 1000s when it hangs?
Have u brought it in for repair? Seriously contemplating bringing it to the apple authorised people. No official apple store where I live. I am now afraid its gonna take a couple weeks repair time and it still having the same problem or spending time telling them that there is an unpredictable hang. Unfortunately this is my main work machine.
I have a feeling apple may not know whats going on with the nmp.
No, the most recent ones i remarked were:
Kernel_2016-02-09-133204_Mac-Pro
WindowServer_2016-02-09-133205_Mac-Pro.userspace_watchdog_timeout
The most interesting this time, there was a slight hang of everything on screen -
and it recovered itself.
I am not bringing it in for service, just because I do not have something to point at, saying "do replace that". Many years ago I did that game with Apple and an clamshell iBook. On battery it just switched off - woosh. Service "did not find any error". Got it back - the error was still there - servicing it again - nothing found - got it back - error was still there. I agree with the statement here above, that Apple has absolutely no clue, what is the SOURCE of the problem. So instead of fixing it in service, they are tinkering something, finally pointing at me, saying that I am "holding it the wrong way".
Yes, I am somewhat disappointed about Apple. But as for now, the software tinkering seems to be somewhat successful in my case, because it is definitely becoming better. So I wait for another sticking plaster.
I do have driver crashes in Bootcamp as well from time to time. But they happen on "normal" PC's as well. "Driver was hanging and had to be restarted". If OS X is managing it the same way - thats ok for me.
I need that machine for working and not for having it in continuos and useless service. As Apple writes in the repair program that the D300 are "not affected", we do apparently have perfectly working machines... I have no time for fighting with Apple.
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The problem looks to be more serious than faulty GPUs. It looks like it has something to do with PCIe management errors that cause problems with graphical drivers. Repair program on GPUs is only getting rid of symptoms not the source of the problem.
The question is: where the hell is the source for the problem?
There are not only problems with graphical drivers. All of Thunderbolt crashed in the past in case of a crash. I do have an Elgato Thunderbolt Dock V1. Everything on it was dead after a crash until reboot. Graphics itself could be recovered by unplugging and plugging the TB monitor again (stuttering picture, but ok for a proper shutdown). But devices connected to the Dock did never recover.
And: No I am not really mad - just making the best of it