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

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

M537 (VXPro)
Yes !
Allows 2.5V only. So use proper cooling.
2x (is 6x) with 66MHz. The board allows 75MHz too, so you can use a 450MHz K6. The BIOS does not automatically recognize the CXT core of your K6-2CXT or K6-III. You can set the support manually with the tool setk6 from ftp.heise.de.