I have a nice 486 motherboard G486VPA with VT82C496G chipset. When I first installed it and played Duke Nukem 2, my turbo button worked fine (the game slowed down considerably). I have been installing other drivers and software since and have noticed that the button stopped working since.

I have made some digging and found a tip that with some chipsets the turbo switch doesn't work while using EMM386.EXE. I have tried to disable it from the CONFIG.SYS file but with no luck. When I press the button the turbo LED actives and deactivates properly so I assume the motherboard receives the information about the turbo mode. I just don't have any idea where to look next. Did I fry some circuit while installing new hardware? Is that even possible?

EDIT: The CPU is Intel 486DX4 100MHz (write-back cache variant). I've made sure that the turbo switch is set to "Turbo" in BIOS (default value was "Suspend").

One more thing - one of the things I did was that I have flashed the BIOS with a newer version. Could that break it?