On 2009-09-16, Zero Tolerance wrote:
On Tue, 15 Sep 2009 04:21:51 -0700 (PDT), "Man at B&Q"

It's taken 20W from the mains supply. How is that "free"?

You can't take 20 watts, then get 20 watts worth of use (e.g. CPUs,
processors, spinning discs, etc) out of it, then still have 20 watts
left which is magically converted into heat. That's not how it works.
There are losses at every stage of energy conversion.

You seem to be missing a rather fundamental law of physics - conservation
of energy: you cannot create or destroy energy.

All the energy that goes into a computer remains in existence for ever.
It is merely converted to a different (less useful) form.

The laws of thermodynamics are also applicable - doing useful work
increases the entropy of a system (i.e. produces heat).

--
David Taylor