Im having the exact same problem came accross this post but unsure of how to do it
Thanks Jack, that worked perfectly.
Here are the instructions that Jack gave me, hopefully helps others out there with issue.
The reason why it won't POST was because both the BIOS and the Intel ME Firmware needs to be updated before it will POST with the new Haswell. I have hence prepared a quick update package to save you the trouble with this update. Here is how to use it:
1. Download the USB Boot Maker and the BIOS update package from the link below:
https://drive.google.com/folderview?id=0B926mvzob6fcdEZtZVN4TmptdVk&usp=sharing
2. Extract the USB Boot Maker to your desired folder.
3. Plug an USB pen drive into any USB ports.
Note: All data on the USB pen drive will be lost after this process.
4. Run HPUSBFW.exe as administrator, check the "Quick Format" and "Create a DOS startup disk", and point "using DOS system files located at:" to the "HPUSBFW" folder, then click "start" to make a bootable USB pen drive.
5. Extract everything on the H81M-PLUS update package into the root directory of your USB pen drive. You now have an USB update pen drive.
6. Connect the USB update pen drive to your H81M-PLUS motherboard, and boot into it on your board with an older processor.
7. Wait till it finishes the update.
8. Your motherboard is now ready to accept the latest Haswell processors.
Hope this helps.
Thanks again Jack.