DC7900 microcode into a... DC7700. Is it really possible?

[Dioxaz]

Hello everyone. My question is directly related to those 2 threads:

https://h30434.www3.hp.com/t5/Desktops-Archive-Read-Only/HP-DC7700-is-Quad-Core-Ready/m-p/7050972#M5...

https://h30434.www3.hp.com/t5/Desktops-Archive-Read-Only/Upgrading-a-DC7700-processor-CPU/m-p/705095...

User Necrolatry claims to have updated his DC7700 microcode with one for a DC7900 with only use of Flashbin and a bootable USB. He didn't give any more details or prerequisites to make the operation successful. In my own case, Flashbin simply refuses to find any compatible image to flash (which is to be expected). So I'm allowing myself to have doubts about his claims.

Did any other person succeed in doing the same? Did anyone try what Necrolatry did? Is there any way to force an "incompatible" microcode to be flashed regardless? And before you all jump on me, this is simply for curiosity that I'm asking. I have 2 of them lying around which are used as media centre PCs. They are fine as they are, and that would be nice if they could be upgraded without me having to hunt on Ebay for motherboard swap candidates.

Edit: Thanks to lolo121's indications after I contacted him, I was able to flash a DC7900 and even a DC7800 microcode! The key is reniming the image file so it matches the BIOS type. If the computer is U786E then the microcode image has to be U7E_XXX.BIN where "XXX" can be any number. Flashbin will then process the file and attempt to flash the microcode. However, it only worked on one of my 2 DC7700 SFF. One was acting as if it had flashed but hadn't while the other did flash successfully. While it still doesn't seem to be accepting my Q6600 anyway (I still get the dreaded 1802 error at startup), that looks encouraging.