> using a 1.67 PowerBook I find in some cases that what I want is a
> faster system speed in general. I'm talking about [...] a greater
> ability to perform multiple (program processes) simultaneously.
> But this I guess is due to the legacy of the amiga system in general.

Not in your case, as your PowerBook only has 1 CPU core/thread anyway, so a modern SMP-capable OS wouldn't run any faster just because of that.