It is completely normal for your CPU usage to go to 100% when using
certain programs.
Programs are given processor time by the OS when they are actually
computing or processing something (that is, not while they are waiting
for a user input or similar). Some programs tend to use all the
processor-time they can get. Examples include games, some multimedia
applications, graphics software (eg running complex filters on an
image), sound processing, video file processing, and so on. These are
programs which process large chunks of data and don't need to wait
around for user input or I/O.
Other programs spend almost all their time waiting for user input - this
would include your word processor, for instance. They have a low
processor utilisation.
If there is only one program that is "asking" for the CPU, it will get
all the available processor time until it has completed its task or has
to wait on something else. This is exactly what you want - when
applying a filter to a graphic, you don't want the processor wasting
time unnecessarily.
If several tasks are "asking" for processor time, the OS divides it up
between them.
If no tasks are asking for processor time, the OS runs the System Idle
Process. This is because it isn't actually possible to stop the
processor dead (not in PCs, I mean). Instead you have to give it a
simple loop or similar to use up its spare time.
With respect I think you might be mistaken in thinking your CPU didn't
sometimes go up to 100% until recently. Like I say, it is not a sign of
something being wrong.
HOWEVER - there is one important possibility. When a program is
accessing the hard disk, it has to spend a lot of time waiting around
(i.e. below 100% utilisation) because the hard disk is so comparatively
slow. BUT - if you're running an on-access virus scanner, for example,
the data stream from the disk is scanned for virus signatures. This
uses processor power, which means that disk I/O is much more processor
intensive. So instead of the processor idling while the file is being
read from disk, it's having to work quite hard.
So, if you've installed an anti-virus package, or some other sort of
security software, you will almost certainly see a high, or 100%,
processor usage far more often.
I honestly don't think this is anything to worry about.
Staiger
