Mark A said:
Yes. The extra CPU core just sits there unless you are running two
applications at once, or a single multi-threaded application. It is very
hard to design multi-threaded applications since the programmer has to
split the workload into two (or more) pieces and then reassemble the
results back into a single result. There is extra overhead inherent in
this type of application design (reassembling the pieces into a single
result), so it is not used unless the tasks are fairly intensive.
Not quite.
The system will still do it's own 'housekeeping' on the second processor.
So IDE I/O, software RAID calculations etc., will give a slight advantage
over a single processor. The biggest gain in this form, is when you have a
single application that likes to hog 100% processor time, when you will
still see the a fast keyboard response with the dual core system. Software
RAID, and file compression (if using a compressed drive on XP), are two
things that give more gain. However these all come at a slight 'cost' from
the more complex kernel.
For most desktop users, given a fixed amount of money to spend, they
would see much better performance with a single faster CPU, than a
multi-core CPU. As I said previously, there are some exceptions with a
some professional multi-media and design applications specifically
designed for with multi-threading.
The 'rule of thumb', is that when using non multithreaded applications,
you will see between 20%, and 40% performance gain, unless the application
is unusual, and is almost entirely 'memory based', when you will see a
slight loss because of the extra kernel overhead. Unfortunately, some
Windows applications are this way inclined... The biggest gain though
comes with multiple applications (which is a thing very rarely 'done' in
Windows - how often do you leave an application 'processing' a major
mathematical task, while you run something else? - generally Windows users
'task jump', running just one task at a time, but with several 'active'),
or with a properly written MP application.
If you Google this subject, you can find reviews that back up what I
said. Some applications (like Office) may actually slower with dual-core
CPU's.
Though, they still respond better to user input.
Generally, unless running an MP application, expect small gains, rather
than large ones.
Best Wishes