~misfit~ wrote:
Apollo wrote:

Matt Giwer wrote:

As to cost, you cannot be drawing more than the wattage of your
computers power supply, probably closer to half unless you have four
hard drives and peripherals drawing power.

200 Watts X 24 hours = 4.8 KW-HR X cost per kw-hr

Most new psu's are 75% efficient at best, older ones even worse, so a
200W psu, under full load, draws about 250W. I do agree that
consumption at full load with only 1 hd and a low power gpu is
probably around half or just over half of the stated consumption.

A Pentium 4 PrescHOT CPU alone will use well over half of the abovementioned
200 watts, before you even consider the losses in the PSU and mobo
power-regulating circuitry before the power gets to the CPU. Close to 150
watts for the CPU alone. Then you've got to get the heat out of the case.

It all depends on your CPU. A PrescHOT has a thermal dissapation of about
103 watts so it's fair to assume that it's using at least that amount plus a
little more. Motherboard circuitry uses a fair few watts (have you ever put
your finger on the power FETs on a running PC, or wondered why northbridges
have heatsinks/fans?) as well. An AMD XP Athlon 32-bit dissapates around 83
watts. You can expect 5-10 watts consumption from CPU fans. These figures
are for non-overclocked machines. You mention the efficiency of PSU's but
then there is the efficiency of the on-board power regulating circuitry as
well (the aforementioned FETs) that supply the low vcores in the range of
1.5v from 12v. Then there's the GPU. Ok, SETI-farm boxes wouldn't have much
in the way of graphics power usually. However my main machine is only
running a nVidia ti4200 and, even on idle (desktop) with it's great big
heatsink and fan, it runs at 53°C. That must take a bit of power to get it
to 53° despite the best cooling Leadtek could devise. Even my SETI machines
run a basic 8MB S3 AGP card and the GPU on those, while not heat-sinked,
gets quite hot to the touch. I have good case cooling, another 25 watts or
so. (I have nine fans all-up in my main PC, *far* more than 25 watts worth).
Even my southbridge gets hot, I have fitted a passive heatsink to it as it
was uncomfortable to hold my finger on it. Then there's the HDD, the RAM
also uses power (I've heard a figure of 15-20 watts mentioned for 512MB).
You'd also be running a modem or a NIC, at the very least (even if it's
on-board). They consume electricity too.

Taking into account the efficiency of the PSU and the mobo circuitry I think
that the 200 watts mentioned is a fair middle-ground estimate, considering
some people will be running PrescHOT's, using more than 200w and some will
be running Celerons or Pentium M's, using less. All, if running SETI, will
be using maximum CPU power all the time. (If the servers are up g).

With all that said temperature is because of watts/area consumption.
With chips it is proportional to gates/area.

I based it on power supply rating and assumed it could power a fully
loaded PC, thus the four HDs. The wattage rating is on a plate on the
PS. Two of mine read 250 and 300 watts. I presume there are no trick
considerations in the rating.

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