A lot of old boards have Asus' custom ASIC 97127, 98127, 99127
There's limited information on what they actually do.

As part of extracting pcbs/schematics from old boards (see sig) it was necessary to figure out wtf this did.

Key assumptions:
1) Asus built it to save parts.
2) Like most things in computing, it was an evolutionary product, not a total revolution each time. Ie, the 98 and 99 were built on top of the 97.

Sources:
440BX/GX reference design
440BX/GX design guide
Bx/pii4x datasheets
Asus boardviews (see sig)
99127f datasheet (attached)
Other boards by other companies eg MSI
Comments on various online sites.

Learnings:
Most of the 97 seems to be basic logic gates implemented in the BX reference design. Some seems custom but not strictly necessary for a board to work.
The 98 and 99 seem to add hardware monitoring and are compatible with Winbond/LM79
The 97 doesn't have HWmon. That one comment you will google is wrong.
I expect the 98 and 99 to be basically the same but with the HWMon and different pinouts.
97,98,99 appear to be the year of design/production.

Attached:
My attempt to copy-paste bits from the reference design to functionally replicate the 97 ASIC pdf and kicad
99 datasheet

Notes:
I haven't boiled it down to the raw guts, of what exactly is in the chip vs on the board.
Some is missing/unknown/I don't care about
I could be wrong, but I'm pretty sure the important parts (like power on etc) are correct.
Probably worth noting that the 97 has a lot of NC pins. That's why they're missing. If they did anything they weren't implemented in any of the boards I've seen.

If anyone feels like QAing it, be my guest 😀