Multiprocessor system VS one processor system

[Artem Koutchine]

Hi!

I need to understand something very clear.

As I understand FreeBSD (as of 4.9) runs one process
per one CPU. This means, that if i have dual systems
with 500Mhz CPUs one process can never run faster
than on a single 500Mhz CPU. However, if i substitute
those two CPUs with one 1000Mhz, that one process will run
twice as fast than on dual 500Mhz, however, to box will
become a bit less responsive, because in a dual box
when one CPU is loaded, another one may have some
spare time to respond. However, in case of very loaded
box both CPUs a extremely loaded and the box will
be as responsive as single 1000Mhz CPU  box 100% loaded.
So, according to what i just said there is not real reason to
setup a dual CPU box under FREEBSD unless you want to
have 5000Mhz box, but there is no CPU with such speed, so
you put two 2500Mhz CPU in it and if you are running a lot
of processes with short run periods you will get overal
perfomance somewhere near 5000Mhz. However, when i 
subsituted two 500Mhz CPUs with 1500Mhz one (even with
less 2nd level cache) on a heavy loaded web server i notice
that sites started to load faster. So, it seems as 
one 3X Mhz  CPU is faster that two X MHz CPUs, at least
for web server with sql base and many perl scripts.

So, there are two questions:
1) Am I right or am wrong?
2) Does FreeBSD 5.X  run one process only on one CPU
or it can run on thread of a process on one CPU and another 
thread on another CPU?

Regards,
Artem