Why isn't Leopard utilizing all cores?

[Qion]

While decompressing a file, I noticed that my system was only using 100% of one of the cores instead of 100% of all four cores. Why wouldn't it use all four and get the job done that much quicker?

[lurk]

Because the program, bunzip2 in this case, is not multithreaded. If the program only has a single thread it cannot be automatically parallelized and run on separate cores.

Now if you have lots of things to decompress you could start 4 instances to use all four cores.

[Qion]

Thank you for the explanation lurk, it seems so obvious now.