underlocking sometimes is useful
I had an apollo 1240 040/40mhz,
in this case this turboboard comes with 80mhz crystal and uses a fan because CPU works so hot and freezes without the fan
once time I was bored and I replaced the 80 mhz crystal by a 50mhz crystal I take from an old PC mobo
the turboboard was rock stable at 25mhz and I had the advantage it didn't require a fan because the 040 was working colder
