Before 2002 (AMD's Cool'n'Quiet) and 2005 (Intel's SpeedStep) CPUs didn't do any frequency scaling for power savings. When the CPU wasn't asleep it was running at it's full voltage and clock speed. While the HLT instruction kept let them 'idle' they only used marginally less power than when active.
So running distributed.net or Seti@Home was using unused processing capacity for a marginal increase in power draw. If you ran them overnight with your monitor (CRT typically) your computer was drawing less power than if you were sitting up all night on IRC or playing Quake. This changed once frequency scaling was commonplace on desktops.
So running distributed.net or Seti@Home was using unused processing capacity for a marginal increase in power draw. If you ran them overnight with your monitor (CRT typically) your computer was drawing less power than if you were sitting up all night on IRC or playing Quake. This changed once frequency scaling was commonplace on desktops.