Pb of CPU use under PT10 with Retina

[kolargol]

Hi All
and wish u the best for this 2013 years, musically of course :)

So first my configuration:

PT10.3.3
Macbook Pro Retina 15"
DUET 2 (working at 176kHz & 24 bits)
2 hard drives on USB3 (but not used for pro tools 10)


My problem:

When i work on a song (only a song not many...) and w/o plug-ins:
I have regularly a message which appears:
"overload CPU, plz increase the level of % of the charge per CPU"
(something like that... sorry it is written in french...)

I tried many configurations, right now i am on 8 CPU/90% of use...

what is funny it is that my CPU monitoring doesnt show me an overload CPU when it happens (only 15% are in use...)

>>> I have a great configuration i think and i cannot work it normally on my favorite program...
Is it normal?

Cheers

Thx for ppl who will take time to help me