Same issue on an 8 core Mac Pro, OS 10.5.6, 10GB RAM running VE3 with Digital Peformer 6.0.2.
Always goes snap crackle and pop with the 4th instance (even when the 4th instance is reduced to just one instrument).
Looking at the Activity Monitor there is loads of RAM free and the crackles and dropouts do not align with any spikes on the Disk IO graph. Peculiarly when the single (simple) instrument in the 4th instance began to play with the other instruments the CPU activity went up to about 85% on all CPU meters in parallel and stayed there. Muting that instance gets the CPU down to around 25-30% on all meters and each meter varies somewhat independently rather than in parallel. Could this be an issue with the way in which instructions are assigned to the multi-core processors? Maybe something that's fixed in Snow Leopard / Grand Central?, and/or in VE Pro?
I'm having to work around by freezing tracks to ensure no more than 3 instances, which is far from ideal.
One thing I don't understand is why the disk speed matters for VE3 at playback time (not load time). Aren't the samples loaded into RAM and accessed from there?
My previous project was much bigger, and required more samples, so I had to work with the DAW on Mac, and the VE3 host on 64 bit Windows XP. This 64 bit Windows instance was running inside VMWare Fusion which was running on the Mac Pro described above. Even with this setup, it was possible to have 4 instances running with a dense piece and no crackles or dropouts. I didn't think it was necessary for this project as the RAM requirements are much lower.
Any thoughts anyone?
Thanks!
G