Ahh, it was Asrock AND MSI, here’s the two threads. Right now I don’t have time to skim through, but I will later, for now, if you will look through each, especially the MSI one (but do look through both) and see what I did for success then let me know it will help me do it quicker later.
Trying to boot a Xeon E3 1270v5 on Asrock z170a-x1/3.1 (Help) (2)
Xeon E3-1240 v5 working with MSI Z170-A PC MATE but with bios reset on boot
^^ This thread, for this exact board and V5, all 4 BIOS I posted in post #22 run w/ Xeon, but unsure his model/your model right now, may need to re-edit those with microcode for your model (not looking at any of that right now, no time)
* Edit @Jonno - Yes, I just checked those BIOS, all x4 compatible with your CPU E3-1225 v5 (506E3), and already confirmed working on that thread 
And I see, ME Does need disabled, but via HAP Bit set only (not sure if that still causes 100% fan)
* Edit - Do you have flash programmer? What is your current ME FW version, check with HWINFO64 as mentioned below, and send me fd.bin as outlined below, then I can tell you if we can downgrade your ME FW/how to flash in those BIOS etc
Check your BIOS’ main page and see if ME FW version is shown. If not then [b]> DOWNLOAD HWINFO64 HERE <
Once HWINFO is open, look at the large window on the left side, expand motherboard, and find the ME area.
Inside that section is the ME Firmware version. Take note of the version. (ie. write it down or get a screenshot)
Once you have that, go to the thread linked below, and in the section “C.2” find and download the matching ME System Tools Package for your system.
(ie if ME FW version = 10.x get V10 package, if 9.0-9.1 get V9.1 package, if 9.5 or above get V9.5 package etc)
> DOWNLOAD " ME System Tools " packages HERE <
Once downloaded, inside you will find Flash Programming Tool folder, and then inside that a Windows or Win/Win32 folder (NOT x64).
Highlight that Win/Win32 folder, then hold shift and press right click. Choose “open command window here” (Not power shell! >> * See Registry file below *).
If you get an error, reply to this post with a screenshot of it, OR write down the EXACT command entered and the EXACT error given.
((If “open command window here” does not appear, look for the “Simple Registry Edit” below…))
Step #1
Now you should be at the command prompt.
You are going to dump the Flash Descriptor (FD), so type the following command:
Command: " FPTw.exe -desc -d fd.bin "
Here is a SIMPLE REGISTRY EDIT that adds “Open command window here as Administrator” to the right click menu, instead of Power Shell
Double-click downloaded file to install. Reboot after install may be required
> CLICK HERE TO DOWNLOAD CMD PROMPT REGISTRY ENTRY <