Upgrading M93p Tiny With Intel 4785T

[Dante of the Inferno]

I recently bought about a dozen M93p Tiny USFF PCs (all are model 10AB, and all use 65W power supplies) for my office space, as they are easily serviceable, compact, computationally competent (for what they're used for), and cheap. I also purchased some Intel 4785T CPU's for some of the users, up from the included 4570T. The first CPU installed fine on my personal M93p Tiny. The second refused to POST, but it did register a blinking light on the LAN port. I had originally (before even purchasing these machines) come across a disgruntled owner who'd also been unable to upgrade the CPU, eventually determining the cause to be a faulty BIOS update released by Lenovo (it caused the BIOS version and Revision Block to be different versions). His fix was as follows:

1. Download an older BIOS version that matches the Revision Block (apparently, this required determining the BIOS version from the string listed in the BIOS itself, then plugging this into a specific URL, as Lenovo doesn't publicly link older BIOS versions)

• Extract the Flash file to a flash drive

• Power down

• Disconnect everything

• Open up the PC

• Disconnect the storage

• Move the internal jumper pins to CLR CMOS (2 & 3)

• Plug in the flash drive

• Power up

• Allow the PC to automatically flash the BIOS to the lower version

• Wait for the PC to power down

• Disconnect everything

• Move the internal jumper pins back to their original position (1 & 2)

• Reconnect everything

• Close the PC back up

• Power up

• Confirm that the BIOS version matches the Revision Block version

• THEN incrementally upgrade the BIOS (and restart) on specific milestone versions from 2014, 2016, and 2018, until the most recent version listed on the Lenovo website (it says 2020, but it's signed 12-26-2019).

After conducting a census, 4 of 12 were affected by this. So after performing the above procedure on those 4 machines, I also incrementally upgraded the BIOS on all the other machines, such that they all are running the same version: FBKTDBA

So, since that second PC was in use at the time I wanted to upgrade the CPU, I moved on to the third PC, which was among the PCs with the version mismatch. Success! Yet today when I circled back to upgrade that second PC, where all the problems began, ...still no change. I even made sure that the Microcode version was up to date (it's 00000027, by the way).

I'm about out of ways to think of how to resolve this issue and upgrade this machine's CPU to Intel 4785T. Clearly the motherboard supports it, so unless some of these boxes just mysteriously had altered BIOS which whitelisted that specific model CPU, then it has to be something else to do with the BIOS itself. The only physical variance that I can see is that, while they are all0 Model AB with 65W power supplies and modern rectangular power ports, some have grounded and ungrounded power supplies (3 wires and 2 wires, respectively). Furthermore, some of them are assembled in Mexico, Canada, and the US, respectively. The misbehaving PC shows a Mexico assembly, while the third PC shows a US assembly (I'll need to unmount my personal machine to determine its assembly country). Could all of this hassle really be down to a ground cable or a country of assembly? I kinda doubt it, but I'm about out of ideas.

So, what do you think about this mystery? Any assistance is greatly appreciated.

[RealBlackStuff]

If you say/think that the only difference is in the power supply, why not try swapping them (Mexico vs US)?
If the (finished) CPU-update works with the swapped-in Mexican PSU, then that Mex-PSU might prevent a CPU-update but is otherwise fine.
Worst case, get another 3-pin PSU for it.