>
>Here is a calculation I did about six months ago
>
>AMD K6/2 500 MHz (plus fan) 45 pounds Sterling
>Super-socket-7 motherboard 45 pounds
>32M 100Mhz RAM 20 pounds
>Old 486 to put it in 1 pound
>
>To this one should add the cost of electricity. The computer draws about
>40 Watts. A Watt costs about 0.60 pounds per year. For, say, three years
>of computation, add
>
>120 Watt-years of electricity 72 pounds
> ----------
>Total 183 pounds
>
>That's 36.6 pence per MHz; or, since I am writing it off after three
>years, 0.389 pence per trillion cycles.
>
Warning on K6's: As far as GIMPS is concerned they're not too good, because
the FPU is about half the speed of the Intel Pentium FPU. (If you run RC5
then they're as good, if not better, because they have very good integer
units).
This means that on GIMPS effectively you get 250MHz, so you get 73.2 pence
per MHz. So providing you can find an AT form factor PII/Socket 370
Motherboard (which I managed to do last December), you can put a Celeron in
instead, although a 500MHz Celeron costs about £85 instead of 45, you get
back to your 37pence/MHz figure. Also note memory prices have gone up, so
32M now costs about £40-50!! Maybe this is the first time in recent history
the price of a computer has stabilised??
Michael Bell.
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