Steve in Sonar with only one instance of Nebula running Sonars CPU monitor shows a low usage spread evenly across all core with 6 instances running the 1st core is in the red with the remaining cores averaging about 50% moving the mouse stops playback.In Reaper one instance of Nebula is 6% with 6 instances only 12%.
              In windows resource monitor running 6 Nebula instances the 1st core in Reaper averages about 20% with the remaining cores using about 15%,10%,and 8% respectively compared to Sonar which shows 55% across all cores on average.There is no stopping of playback in Reaper or glitching at all with any mouse movement even when Reaper is almost at max with 16 Nebula instances (96%) there's no glitch or playback stop.Reaper averages 11% average CPU use on the windows resource monitor compared to Sonar at 35% average with same number of Nebula instances and Sonar constantly spikes up to 100% stopping playback.

All of this on one track of audio.

Maybe modifying ExtraPluginBufs in AUD.ini will help. If I had to pick a value, try setting to 32
I am guessing this is a 64bit version of Nebula running on a 64bit version of SONAR. I do not have a 64bit version of Nebula to test and did not install the 32bit version on my current machine.

Pict
I use Acustica-audio Nebula 3 which I really like but unfortunately I can't use many instances of it in X3 pro therefore I tried Reaper as a host and to my surprise I could use far more instances of Nebula.I have been using Sonar for a few years now and I have got used to the GUI so I would like to keep using it as I have bought the prochannel modules and I am used to the hardware mixer paradigm but it runs like a slug compared to Reaper.I also use Logic and have done for years but I am reluctant to buy a new mac(as my present mac is only a dual core)just to run the latest version of Logic.Am I missing something in the preferences that would lighten the processor demand(I have a quad core i5 with 8 gigs ram win7 machine)I have the often reported 1st core spiking on the cpu meter.Is X3 just a CPU hog?

Hi 
I had exactly the same issue and always the first core cpu meter was almost hitting the max and the rest of the cores like were useless :) 
I posted a topic and got some clue but still had the issue. anyway, i update my os to windows 8.1 and sonar to x3d it seems problem solved. i think some waves plugins had conflict with windows 7 and x1. Also i realized sonitus reverb which has a great quality but has a bug. any time i add some reverb and increased the pre delay to max i could see the firs core starting to hit the ceiling.  I am using cakewalk when it was new born about 15 years ago or more which the version was 1.4 i believe, i am not sure, till now which i have x3d but I believe we will have much less problem and issue with logic or protools even with a lower spec of PC. The Only reason i still stuck to it because it is very user friendly and i used to it after almost 15 years :).
Long story short, try to run sonar on win 8.1 machine and see the result :)
Good luck
 
Reza

Scook and Reza thanks for the info I'll try the AUD.ini adjustment.As I've said before I've been mainly a Logic user and before that Creator and Notator I really wish that Logic was still available for the PC the notation is excellent,the 90 screensets are great I feel really limited with 10 if only Macs weren't such a ripoff (imo).
    I would love to get Sonar running as smoothly as some of the people on here have it running.I didn't like the interface of the pre X series of Sonar and I thought that with Sonar adopting a more Logic like GUI it would be easier for me to use it but sadly for me it hasn't fulfilled my expectations I really get annoyed having to tweak preferences and registry entries etc but after investing time and money on it I don't want to throw it down the pan but I'm getting close.

CakeAlexS
One is chalk, the other is a cow, the other is Pamela Anderson.... that's just the way it is.

ROTFLMAO!
Love your choice of comparison!

I wonder if up sampling, down sampling, filtering and dither between every instance might explain the difference.

Perhaps disabling 64 bit engine might help?

Thanks for the suggestion gswitz I just tried it but it made no difference unfortunately.

pan laws?

You guys are all exceptionally helpful so I'd just like to restate my appreciation.Infinite thanks and good vibes to you all you are a fantastic example of how a user forum should be.
 
                Now back to the battle