Here’s where it gets interesting. There’s rather a lot happening on the control side of the board.
The big obvious 20 pin IC is an Intersil HIP6004B and sure enough the datasheet confirms that it is indeed a switching buck regulator with recommended applications that include the power supply for older generation CPUs.
What makes this part interesting is the way that you select the output voltage. These days the typical method for setting the output voltage is to use a resistor divider but this device does it through a 5-bit digital input that feeds an onboard DAC.
The other IC up the top left is an LM324D quad op-amp. I honestly cannot think what that’s doing on here and my searching around to find example applications that include such an op-amp array in this configuration yielded nothing. Maybe I’ll be able to figure it out during testing.
There are a large number of test pads dotted around the board but unfortunately none of them are labelled with the expected value.