hardware fixes (AMD K6, K6-2 and K6-III in Socket 7 boards by Tyan)

Tyan doesn't officialy provide support for K6 in old boards. But there are mainboards which can run the K6.

Tomcat 1562s (rev Q2/95 and later)
Yes !
2.65V (J40 off, J41 off, J42 off, J43 on, J44 off, J54on, J53on, J52off)
2x (is 6x) J19 on, J20 off

2.65V is beyond the specs (2.3-2.5V) for the 2.4V K6. You'll need a good cooling kit to avoid overheating.

Trinity S1592s
Yes !

Trinity S1598s
Yes !