C7.5 Multithread processing performance experience?

Well I’ll quote myself from the post I made in this very thread:

J-S-Q “And yes… I know, the ASIO METER IS NOT A CPU METER because this is the (unhelpful) response that is always posted when this issue is raised. But WHAT EXACTLY is the bottleneck here?”

Well done for being yet another person to post this unhelpful response. Now please explain EXACTLY what it is that is causing Cubase to run out of steam when there is still a lot of CPU power left. Or please explain why, on the same computer, Vienna Ensemble can apparently run 12 instances of Altiverb with no problem when Cubase can only cope with 4: