I'm not making an account I'll never use.
I don't know if it's unique to each CPU specifically, because they'd need the UID of each chip manufactured, but considering the i5s I have are both the same, I'm guessing "yes".
For now I'm gonna keep my multiplier at 37 (where it belongs) to avoid damaging my Xeon, used ones are still $300+ and I got mine for three times less than that.
It took about three months, starting the day I posted this (because of work). I found the unencrypted microcodes easy enough from Intel but they're "packed" in the UEFI. I didn't do the decrypting, someone on /r/crypto helped with that. It's like an archive but in a proprietary format by the MB vendor. Some BIOS utilities and UEFI editors can help, some can't.
I used DMEdit to do some digging in AsRock's trunk.
The rest can be done in a hex editor as long as you have the info from Intel that states how the codes work and which do what. Which you can only get FROM Intel. I had to email them for about two weeks to get them for my Xeon, and even then I had to assure them I wasn't going to sell the modified microcodes.
So yes, it's not worth my time or effort, but the knowledge and experience is nice.
Here's the Sandy Bridge pad-out: