The complete question: "I have noticed that when someone is running O and has walked away from their terminal, O still uses about 30% of the CPU on SGIs, but if they iconify the graphics display window the CPU usage is about 0. Is this a feature or a bug ? I.e. is the best way of solving this problem through user education ?"
O is always looking for input (keyboard, dials, ...); therefore, iconify your O window if you're going to drink coffee, or use a Unix command that ties up the keyboard, e.g.:
O > $ sleep 9999999
Hit CTRL-C when you have had your coffee. Do *NOT* use CTRL-Z to interrupt O; it will log you out immediately ... (at least on SGIs it does).
940124: There's now a one-line macro in OMAC (file://rose.bmc.uu.se/pub/gerard/omac/pause.odb) which, when executed, will prevent O from consuming unnecessary CPU cycles. When you want to continue, just hit RETURN. The trick is to force O into a Fortran READ. The macro looks like this:
! pause.omac - Gerard Kleywegt @ 940123 print #Hit RETURN when you want to continue ... #