Jumpers.
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How we used to overclock.
At least that's how I had to do it when I overclocked my 286 from 8Mhz to 12Mhz, my 486sx25 to 50Mhz and all of my Socket 7 Pentium and K6 based systems.
And for this reason we all need to bow our heads and say a prayer of thanks to, the now dearly departed, Abit, whose motherboards helped put numerous jumper makers out of business.