I have tried to use ACPI throttle on many 440BX boards and I've had very bad results with it (anything above a 30% throttle causes an abnormal gameplay stuttering - even though when testing with 3DBench framerates are still high). The issue seems to be linked to sound - which is handled by the throttled south bridge (even though I tried many cards, both ISA and PCI). Anyway, VIA chipsets are much better for this, so I'm sticking with them for ACPI throttling.
The Klamath is hot, hard to overclock and slower than a K6-2/3+ (so might as well just go with the latter)...
There are some Deschutes which are unlocked too, can be easily overclocked/underclocked, but they are harder to find.
2 x Socket 3 / 3 x Socket 7 / 4 x SuperSocket 7 / 4 x Slot 1 / 5 x Socket 370
3 x Socket A / 1 x Socket 478 / 2 x Socket 754 / 3 x Socket 939 / 2 x LGA775 / 1 x LGA1155
Current rig: AM4 - Ryzen 5 3600X
Backup rig: LGA1151 - Core i7 7700k