PC/AT overclocking

[Gordon JC Pearce]

Chris M wrote:
> 
> --- Julian Wolfe <fireflyst at earthlink.net> wrote:
> 
>>> I thought the overclocking craze on the 
>>> PC-AT was a lot more interesting, myself...
>> 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.
> 
>  I overclocked the 286 in my ITT XTRA XP years ago (6
> - 8mhz woopy) by replacing the crystal. Worked fine,
> slightly *noticeably* faster. Am not aware of a bios
> dependency for this hack. In fact, later AT's had an 8
> mhz clock. 
>  I'm a bit behind here. If y'all were talking about
> raising it to some *other* ungodly speed, forgive the interference.

I overclocked a ZX Spectrum by replacing the 14MHz crystal with a 
17.73MHz one.  Of course everything is derived from this, including 
video timings, so I needed to tweak my monitor up proportionately, and 
run a cassette player a little bit faster so the tape speed matched.

It made Manic Miner extremely difficult.

Gordon.