🚀 go-pugleaf

In article <slrn8386n3.e4.piglet@pigsty.td.micromuse.co.uk>, Tim Haynes
<piglet@glutinous.custard.org> writes

>Yup, I'd admit to being relatively pedantic, but *how* does one determine
>whether it's speed that affects temperature *or* the other way round, in a
>given case? (Other than, say, it being you wiggling the thermostat, sort of
>thing!)

Very simple. See how fast you can run an 8MHz 8086 as you decrease the
temperature. You will find there is a maximum rate and that this is very
little affected by temperature simply because the switching speed of the
components limits the maximum clock speed. This is an n-mos chip (ie NOT
cmos) so the dissipation does not tend to zero as the clockspeed tends
to zero. You might like to try an early cmos processor (some 486's IIRC,
and notebook 386's) and compare dissipation (ie current consumption) vs
clock speed where you will find that dissipation is approximately
proportional to clockspeed. In this case it will be very clear that it's
clock speed that *causes* temperature elevation and not temperature that
permits higher clockspeeds.

Really it's only been recent chips that have dissipated enough for the
package dissipation to be a limiting factor in the permittable maximum
clockspeed. Hence the use of lower core voltages in an effort to
restrict dissipation at any given clockspeed (because dissipation is
roughly proportional to supply voltage).

-- 
Oz