John Weiss said:
Linux, Win XP, OS-X... All modern, mainstream OSes can take advantage of a dual
processor. XP Home can even use the dual-core CPU if not dual sockets!
That doesn't help if you need processor power in a specific
application. If that application cannot run multiple threads, it can
use only one processor, and so the speed at which it runs depends
exclusively on the speed of a single processor; adding more processors
will not improve performance.
Most games (and most other applications) are not written to take
advantage of multiple processors.
For gaming, the issue becomes the tradeoff between $$ and raw clock speed. For
most productivity apps, multiple threads make the dual-core option vaible even
at a lower clock speed.
Most applications don't run multiple threads. Multithreaded
applications are much more complex than single-threaded applications,
and since few people have multiple processors, it's not usually
cost-effective to write an application for multiple threads.
None of this is news. Multiprocessor systems have been around
practically since computers were invented, and the considerations have
always been the same.