Multi-Core & Software question

[DrVal]

This has probably been asked a million times, I tried to search and couldn't find what I was looking for....

I guess I just don't understand multi-core processor technology and how it functions with software. When a software is 'multithreaded' does that mean it can use multiple processors for it's computing or is that something else?

Why is it when I use any software that I can throw at it, one of my cores hits 100% and the rest just sit there with a total useage of 50% - does that mean that software isn't multithreaded? If software IS multi-threaded can it then max out all the processors? Would it always use multiple processors or just when it really needs to?

Maybe there's a laymen guide somebody could point me to...

 

[DeathFromBelow]

It sounds like you've got it.

A single threaded application was designed for single core processors. On a multi-processor machine only one core will run the application.

Multi-threaded applications can use multiple processors. They may not use all processors "100%" all the time, and some may only use the other processors a little bit. It just depends on how the program is written.

Most image editing and video editing programs are multi-threaded, and some newer games are too. Windows Movie Maker in Vista/XP is a good example of a multi-threaded application that really takes advantage of all the processors you have.