AMK62-500 with W98

I had a PC with AMD K6-2 500 which failed regularly. I replaced hard drive, cpu fan to no avail. I then bought a new case (with new power supply), new motherboard (Gigabyte Ga-5AX) and cannot get W98 to install with this chip. It fails at various places. If I replace it with K6-2 350 (and reset jumpers) all is OK.
Anybody else had problems with this processor?
(I have a friend with same m/board and same chip and it is OK).