RolyL, where would they get the sound samples from first of all to do the processing? either the RAM or the hard drive. that has to go through the PCI bus, and now through the USB port.
typically sound files in games are recorded in either mono or stereo, then they are sent to the soundcard for 'processing' by the API that the soundcard supports in hardware. otherwise they go to the CPU, which then uses the soundcard as a passthrough device..
so, say a gunshot is recorded for a game. the quality IMHO would be 16 bit 44100hz or so, possibly in mono due to the fact that a stereo sample would seemingly confuse the issue even more.. don't quote me on that though.. not only that, but you have people's voices, people running around and jumping, other types of weapons being fired.. an FPS game seems to use alot of audio samples. many games do in fact.
so the only way for the Extigy to get away with the USB port and play games is to compress (losslessly?) the audio but I don't think that they're doing that.. it would eat EVEN MORE CPU time.
btw, the bitrate of an audio file that is in PCM format (like a wav file, or a CD audio track), is simple to calculate. bitrate = number of channels * number of samples per second * number of bits per sample. so 2 * 44100hz * 16 bit = 1 411 200 bits/second.
Surely this isn't the full story at all? Let's take an engine involving extensions (EAX, A3D etc.) for example. The sound chip has processing to do, else all would sound alike (which they clearly don't) excepting physical factors such as s/n ratio etc.
they don't sound alike because most soundcards use different API's. Aureals Vortex 2 used the well supported A3D 2.0, but other soundcards not based on that chip had to use Directsound (like the Creative labs chips) which uses inferior HRTF.
An EMU10K2 can receive a EAX HD signal and deal with it, a CS4630 cannot.
why do you think that is? not becuase the CS4630 isn't powerful enough, for it can run an API made by Sensaura that is just as capable as EAX Advanced HD but with more accurate (due to better work done by engineers) HRTF, meaning better 3D positional audio.
the CS4630 can't do it, becuase Creative won't let anyone use that API. it gives them an 'advantage' over other cards, becuase it has the potential to catch on as the major sound API for gaming in the PC industry.