Re: Why do CPUs run hotter...?

In article <gCmlg.83170$QU3.70595@xxxxxxxxxxxxxxxxxxxxxx>,
look@xxxxxxxxxxxxxxxxxxxxxxxxxx says...
Most sensible CPUs have a "WAIT" instruction that idles most resources
until an interrupt ocurrs. Pentiums are not sensible CPUs, but they
have something like that, too. If you run a DOS app on a Pentium, that
usually keeps it on hard, since most DOS apps loop all the time.

Windows will show you per-cent CPU utilization, and it's probably
running a low-power wait instruction during most of the idle time.

Yup, just tried it: Win XP averages about 2% CPU load until I start an
old DOS program, at which time it jumps to about 85%.

Can anyone confirm that Windows' idle loop uses WAIT ops?

It does. Since Win98, anyway. Win95 was iffy.

If so, then the CPU really is idle for milliseconds at a time when it's running the idle
loop. Thanks for this interesting clue.

Certainly.

--
Keith
.

Relevant Pages

  • Re: Why do CPUs run hotter...?
    ... Pentiums are not sensible CPUs, ... If you run a DOS app on a Pentium, ... Windows will show you per-cent CPU utilization, ... Can anyone confirm that Windows' idle loop uses WAIT ops? ...
    (sci.electronics.design)
  • Re: Pentium vs Celeron
    ... The only difference between Celerons and regular Pentiums ... amount of very high-speed RAM on the CPU chip. ...
    (microsoft.public.windowsxp.general)