Just in case anyone was having the same problem as I did... This thread ended up saving me!
So I bought a new Supermicro X11DPH-I and a cheap ES CPU just to test the board. However the motherboard came with bios v3.0c which didn't detect the CPU. It would hang on POST with a message saying "PEI -- CPU initialization B1".
Here is how I fixed it:
Downgrade the bios to 2.1 provided in this thread link by
romanstingler. (Motherboards X11DPH-I , X11DPH-T and possibly X11DPH-TQ share the same bios file)
In other to downgrade the bios version, without having a working booting motherboard (I didn't had any other CPU), I went to wiredzone website and purchased a Supermicro Out of Band Firmware Management License (25$). I couldn't find it for sale directly in supermicro web site...
With the OOB license installed it is possible to downgrade the bios with the board powered down (only IMPI running).
It now boots fine, and later when I purchase a better non ES CPU I can upgrade the bios to a more recent version.