This is an old Amd 486DX2/80, fitted with a home made water block. It runs completely stable at 100 MHz (I increased the voltage from 3.3V to 5V). It freezes from time to time if run on 133 MHz.
I made the water block by crossdrilling a block of copper. The top and bottom plates are made from PCB material.
I use a 670 l/h pump. There is no water cooler installed yet. The water gets warm after around a hour of uptime and even after a couple of hours it doesn't get hot.
I have managed to network boot a NetBSD installation.
I don't know the type of the motherboard. All I know is that it uses an Opti 82C495 SX chipset and that the jumpers are similar to Shuttle's HOT 409486VLB. I had to do some reverse engeneering to figure out how to increase the clock and voltage.
This is my chart of the clock generator circuit.