It doesn't work that way. Audio processes use their own CPU interrupt, which SHOULD allow them to have pretty much the highest possible priority. And if you had a dual CPU system, then your idea might work, because each CPU would have its own set of interrupts. The problem with multi-core CPUs is that they share a set of interrupts and really all that's being duplicated is the instruction processing logic. People look at them and see "quad core" and think that it's going to be the same as having 4 separate CPUs. It's not. If you had a 4-way system, the total system responsiveness would pretty much always be very high, since each CPU has its own dedicated data pathways. With multi-core CPUs, each core shares the same set of pathways, so data can still get backed up. The i7 line improves this a bit by connecting the CPU directly to the memory, instead of going through the north bridge chipset. Something AMD has been doing since the first Athlon64.
Long story short, I'd say you're just demanding way too much of a USB sound card. Regardless of what the sound card itself is capable of, you have to remember it's limited by the USB bus latency. People tend to just look at the advertised 480Mbps top speed of USB 2.0, and think that it will be really fast. They don't seem to understand that it's not really intended for low latency devices, since the origins of USB was to replace a lot of the common ports on computers at the time for low bandwidth devices. So PS/2 keyboards and mice, parallel printers, and dialup modems that plugged into the serial port. Along the way they increased the total bandwidth of the bus, but never really addressed the latency issue.
A USB sound card is just never going to be able to handle those kinds of low latencies. It doesn't really matter what you do, you're hamstrung by the limitations of the USB connection. If it were a FireWire (IEEE 1394) sound card, then you would have a fighting chance, because Apple designed FireWire to be a low latency interconnect for things like hard drives.
So you're basically looking at having to buy a PCI sound card or just living with the stutter. And since you're using XP x64, which was never really intended for widespread use (hence the fact that it was only sold OEM, so it was generally understood users would understand and assume the risks/shortcomings) good luck to you in finding a PCI sound card that has XP x64 drivers. No offense, but you've really dug yourself a nice deep hole here, and getting out isn't going to be fun.
Is this possible?
I'm running windows XP Pro 64 I have good specs on this machine, an i7 quad, 12 gig of ram and an edirol UA 101 (usb) sound card. But whenever I open and close an app (well most apps) with any other audio devices running (Windows media player or my Daw FL studio for example) I get severe buffer underruns and my whole system stutters very badly until the apps have finnished their startup, during their startup process any audio playing becomes extremly distorted.
I'd like to find a permanent solution to this problem, a few things that have worked so far were, 1 using a pci sound card an e-mu 0404 (That helped) but I no longer have this card, the second solution was to raise my buffer size way up to arround 30 ms or over, obviously this is not a desirable workaround as this card can run quite happily at latancies between 3-6 ms which I need it to do during normal audio processing tasks such as running my Daw.
So, it occured to me that isolating all the audio processes to a single CPU core might stop the distortion/interuption of the audio signal that I'm expieriencing, but from here on I'm a little stumped, I can't find any trace of any processes that are linked to my sound card, or any audio devices at all infact, none of them show up in my task manager.
Isolating the apps themselves didn't work, isolating the sound card seems impossible, am I perhaps barking up the wrong tree here?
Any advice would be most welcome.