PC/AT overclocking

Chuck Guzis cclist at sydex.com
Fri Nov 10 15:21:24 CST 2006

On 10 Nov 2006 at 14:23, Julian Wolfe wrote:

> Apparently on the AT model, you needed to have an early (1984) BIOS to make
> it work, but yeah, I know the CPUs in the one I have are 10MHz bumped down
> to 6.

There were stories of some folks clocking the 286 as high as 20 MHz. 
I think IBM didn't want to be saddled with the support issues that 
overclocking entailed, so they modified the BIOS to make the clock 
speed check.  If you knew someone with a PROM burner, it was easy to 
patch out, however.  Or you could kick the clock up after POST.

Some early Taiwanese PC clones had a jumper-selectable Turbo mode 
that simply switched oscillators (or crystals) to a higher frequency. 
 Very crude--the time-of-day clock would run way too fast without a 
TSR to scale things back.

That brings up an interesting question.  Who was the first to apply 
the word "turbo" to a CPU?


More information about the cctalk mailing list