Cross-flashing retail BIOS to HP Prebuilt

I recently picked up an old HP 285 G3 Tower PC from an auction site that I’ve been playing around with, specs as follows:

AMD Ryzen 3 2200G
8GB DDR4 RAM
256GB NVMe SSD

It has a proprietary HP AM4 motherboard with an AMD B350 chipset. Now, according to AMD, this chipset can support up to Ryzen 5000 series CPUs, but only with a compatible BIOS. HP never bothered to release a BIOS for this board with the ComboAM4 Agesa to support the newer CPUs, so it’s stuck with 2nd Gen Zen+ Ryzens as the newest CPUs officially supported.

It would be nice if I could put at least a Ryzen 5 3600 in there, so I had a crazy idea: Most B350 retail boards have BIOS updates that support the newer Ryzens, what if I took one of those from a similar B350 board and flashed it to the HP board?

I have a CH341A programmer, so it’s not a problem to flash an unsupported bios and recover from a backup if it doesn’t work.

I chose this board from Gigabyte as the most similar B350 board I could find GA-A320M-S2H V2 (rev. 1.x) Key Features | Motherboard - GIGABYTE Global

My rationale for this being:

-Both boards have 2 RAM slots
-Similar rear IO
-Similar PCIe / NVMe slot arrangement
-Both use SuperIO chips from ITE (though not the same model)
-Both use an AMI UEFI BIOS with a 16MB ROM

Realizing I had a low chance of success, I flashed it and powered on the PC. I could’t get any display output with a monitor connected to the analog VGA port on the integrated graphics, but I got a single “beep” from the board and the HDD activity light was blinking. So I put in a PCIe graphics card and tried again, and sure enough the PC booted into Windows 10 from the SSD.

USB keyboard & mouse seems to be working correctly, the date and time was correct, and I was able to get into the Gigabyte BIOS setup. The only issue is, the PC restarts itself every 30 seconds or so, so I haven’t been able to check much else.

I realize this is a shot in the dark, but does anyone have any ideas how I can fix the restarting issue? All the fans are spinning normally, so I don’t think it’s overheating.

Hi, did you end up solving this issue? Im trying the same thing.

Unfortunately not, I had to reflash the stock bios and have since sold that system on.

On a similar note though, I now have the slightly newer HP 295 G6 tower which I was able to flash with the BIOS from the 295 G8 using the CH341A programmer, and this is completely stable, so it can work in some situations. It looks like the motherboard in the G6 & G8 is practically identical.

Using the G8 BIOS has unlocked support for Ryzen 5000 chips, whereas the G6 BIOS only supported up to 4000 series.