On a multi-core machine with threading, especially when using highly scripted and/or sample intense instrument, you should place the bigger instruments in their OWN instantiation of the VI. Other instruments should be in THEIR OWN instantiation. IOW, if I am running Kontakt with a highly scripted slide guitar in slot one and then place a complex piano in slot two, that can hit the CPU pretty hard.
If I put the slide guitar by itself in on instance of Kontakt and then create another instance of Kontakt with just the piano in it, DP will use separate cores in the machine to process each instance. Otherwise, both the guitar and the piano are being processed by a single core and the CPU takes a hit.
The easy way to remember this is that each instance of the VI should have it's own fader in the mixer. It doesn't matter if it's in a V-Rack or not, just that the VI has only one instrument for the "heavy hitters."
If you have some instrument that are not that intense, you could still put those in a single, multi-channel instance of the VI and you should be OK. But agin, if the instruments are large, heavily scripted, or have a high number of samples to process, then EACH instrument (patch) should be in it's own instantiation of the VI in question.
This come right from the mouth (fingers?) of Magic Dave at MOTU and he knows pretty much everything there is to know about this stuff. He plays a pretty mean guitar, too...
You gotta love DP...
