Hard to be positive here, because it all depends on the actual
implementation on the motherboard. For example, if the USB and Firewire is
simply provided via third party chipsets, these are probably connected via
the PCI bus anyway. And since the add-on card is also using the PCI bus, in
the end, there's really no difference. Both will have the same level of
performance (assuming their respective chipsets are comparable) and require
the same level of CPU support.
I assume you're considering this possibility because you're comparing, for
example, the benefits of using a PCI sound card rather than on-board sound.
But there's a difference. On-board sound solutions are typically *far* more
CPU intensive, by nature, than USB or Firewire (e.g., decoding an audio
stream). In contrast, these latter *interfaces* are just that, simply
interfaces. They don't require vast CPU resources. Their biggest problem
is saturation of the PCI bus! This is why Intel introduced CSA w/ the 875
chipset, to bypass the PCI bus for LAN traffic, thus relieving some of that
PCI congestion. It's very possible the integrated USB and Firewire solution
is *superior* to a PCI solution *if* such a solution is also able to bypass
the PCI bus. I'm not saying it does, only that the integration of
components on the motherboard makes it more *likely* that such optimizations
can be applied (ala CSA). Once you move to a PCI solution, you're *always*
hampered by the PCI bus, minimally. Could the PCI device use some form of
DMA to bypass the CPU?? Maybe, highly unlikely though, not for a simple USB
or Firewire card, but there's no reason to believe the on-board
implementation wouldn't so the same!
In the end, I doubt seriously that foregoing the on-board solution for the
PCI solution will afford any benefit here. It will likely either be the
same or even worse. The problem for *these* interfaces is PCI bus
congestion, NOT CPU utilization. Something like PCI Express is the solution
to that problem, by providing more bandwidth to the PCI bus. The only real
possibilty for better peformance (if not less CPU utilization) is if the PCI
solution uses a better chipset. For example, the VIA USB chipset is known
to be a mediocre performer, and one would assume VIA motherboards use it as
an integrated solution. If you then installed a NEC PCI USB card, known to
be a very good performer, well, in that sense, the PCI solution might be
better. But I don't believe either solution would have much impact on the
CPU.
HTH
Jim
