Sorry to step into the discussion but may i suggest this ( -nehalem_error_disable ) boot arg being added to Clover / Configurator ( so people get to know it ) , which i accidently discovered today by digging around AppleTyMCEDriver binary
right hand side top to bottom:
-nehalem_error_disable disables the AppleTyMCEDriver
offcourse works perfect in 10.13( dunno about older Versions ) and gets rid of the panic on MacPro4,1 and 5,1 at the ECC ram check.
Pls ignore this if it is old cheese but i couldnt find anything about it so i thought id share it.
And it is a nice addition to the other workarounds to this old little problem.
shanee u could try Shiki/NvidiaGraphicFixup Combo + Webdrivers Inject maybe gets u anywhere or its the AppleTyMCEDriver messing with ya, depending off course in what smbios was used , but as far as i rem Nvidia fixed the ECC Ram Problem with the Webdriver ...not sure but maybe helps somehow.
dont do it thru the appstore ....download combo update 10.12.6 from apples website ...whilst browse to System/Library/Kernels and make a backup of your kernel ....
once its downloaded mount dmg install update ...dont restart when prompted.... now open above DIR again and copy your backup init ... done.... now you should be able to reboot with 10.12.6 if the kernel for 10.12.5 somehow will not work ull have to wait for bronya to cook a new one or read for workarounds ..but in 8 out of 10 cases older kernel work with newer updates ...good luck
How can I change display priority?
With 7xxx GPUs or newer you could simply add connector-priority GPU controller property with sense ids (could be seen in debug log) in the order of their importance. This property may help with black screen issues especially with the multi-monitor configurations.
Without this property specified all the connectors will stay with 0 priority. If there are unspecified connectors they will be ordered by type: LVDS, DVI, HDMI, DP, VGA. Read SSDT sample for more details.