There are a couple of reasons for my question
1) I bought a ST 486 CPU, because of sentimental reasons, but it hangs when tried in either of my two 486 motherboards. One time it did boot into DOS.
2) I recently mistakenly bought a new wrong 486 motherboard (I meant to buy one of a similar price from the same seller) via Ebay and to my horror can find no information on jumper settings. It came setup at 40MHz and does boot, but I have been unable to change it to any other frequency.

I have also bought a second new motherboard, a Chicony CH-498B rev 2.0, the one I intended to buy, for which jumper settings do exist. This board, unlike my others, can support non 5V CPUs.

The Chicony motherboard has a lot of jumpers, and in the instructions (thank you whoever scanned them!) the CPU jumper table is quite complicated. There are 12 different setting groups, such as for...
1) Intel 486SX
2) Intel/AMD 486DX/DX2
3) Intel 486DX/DX2 SL (I've never heard of the SL)
4) Intel 486486DX4
5) Cyrix 486DX
6) Cyrix 486DX2
7) AMD 486DX4
...etc...
and there are 9 groups of jumpers.

I reaslise that some of the jumper settings will be used to select the clock generator chip. On one of my boards this chip has 4 pins for frequency selection, I buzzed it out with a multi-meter as I had no settings for that board either.

But what are all the rest?

Where does my ST(Microelectronics) CPU fit into this list, as it doesn't have an entry.

Are the pinouts for all 486 CPUs identical, or do some pins differ, if so what pins and what do they do? I had naively assumed that all 486 CPUs were pin compatible, but I now wonder...

If I can try to trace from some CPU socket pins to jumpers, then I might be able to figure out at least what some of the many jumpers are used for.

I have identified the clock generator IC, a KDN-0147C, but cannot locate a datasheet. Pins 7 and 8 connect to the 14.318MHz xtal just to the left.
The middle pin of the jumper immediately below (JP31) goes to the CLK pin of the CPU socket. The outer two pins currently have 20MHz and 40MHz, but when I select the 20MHz side, the board fails to operate.
I have randomly changed the jumper positions in the big block at the bottom, but have never succeeded in changing the frequency from 40MHz.

The chipset is and Ali M1429G, and I suspect some jumpers connect to this IC. Again I have been unable to find any datasheet whatsoever on this IC. Also was surprised to find that no 486 motherboard schematics have found their way onto the internet, I guess they were just a little before it took off and before the days of PDF, otherwise I perhaps could have used a schematic as a reference.