CPU Error (-6101)

[Connor]

Hi. I have an Early 2011 MBP 15" 2.2ghz QuadCore. Running Pro Tools 10 on OSX Lion 10.7.2

I would like to know why is it that when I am running a session (with around 1.3GB of samples in Kontakt, some synths and Battery) I get these CPU errors. (NOTE* These errors only happen when I am using samples/VI's)

I have set my playback engine to use 7 out of 8 cores.
I am on 256 HW Buffer Size.
CPU Usage Limit is 85%.
Delay Compensation is Long

Now obviously the answer would be : Your machine is too slow. BUT

My activity monitor shows that my cpu is on average 78% idle.
3-5% is used by the system.

How is it that Pro Tools can only use around 20% of my cpu?

On the other hand... When working on a post production session. I have over 50 stereo tracks with a large amount of waves plug ins and sum buses with convolution reverbs, I get no errors at 256. AND my activity monitor shows that pro tools is taking up a good 50% of my cpu.


It seems that Pro Tools likes working with audio a lot more than midi/sample based stuff. But why would this be the case?
ALSO... I have a song multitracked in pro tools. EVERYTHING is audio except for Alicia Keys Piano Samples in Kontakt 4. Im playing at 256 completely fine. THEN the piano gets introduced in the song... it plays it .. and then when u think ur safe. bam! another cpu error. Then i skip ahead where there are no more samples being played... and viola! no more errors..


I just want my system to be utilized properly (I didnt spend this much on a fast computer for it not to be utilized.) and when I am running into CPU errors on pro tools.. but my activity monitor shows only 20% is actually being used by Pro Tools.. something is wrong.