Bonjour,
Thanks for your support 😊, yesterday I tested the IME 8.0.4.1441 of the iMac 2012 (With my Xeon Sandy Bridge CPU), it seems to start (with a beep like in an official firmware update), no graphic card to help, but a priori no network at all, (tested with several blind systems).
I'll have to wait until I get a new graphic card to go further.
Too bad I don't have a real expert to help me, I'm at the end of the possible tests, it's frustrating.
I might have to change the eeprom by an extractable one because by dint of testing I might break the soldering (I broke 2 motherboards like that), if I can be informed about it!
Bonne journée.