User Manual

Mbox User Guide20
CPU Usage Limit
The CPU Usage Limit setting controls the per-
centage of CPU resources allocated to Pro Tools
host processing tasks. Used in combination with
the Host Processors setting, the CPU Usage Limit
setting lets you control the way Pro Tools tasks
are carried out by the system.
•Lower CPU Usage Limit settings limit the effect
of Pro Tools processing on other CPU-inten-
sive tasks, such as screen redraws, and are use-
ful when you are experiencing slow system
response, or when running other applications
at the same time as Pro Tools.
•Higher CPU Usage Limit settings allocate more
processing power to Pro Tools, and are useful
for playing back large sessions or using more
RTAS plug-ins.
The maximum available CPU Usage Limit de-
pends on the number of processors in your com-
puter and on the number of processors you spec-
ify for RTAS processing. This value can range
from 85% for single-processor computers, and
99% for multiprocessor computers (which dedi-
cate one entire processor to Pro Tools).
On multiprocessor computers, the maximum
CPU Usage Limit is reduced when you use all your
processors (as selected in the Processing pop-up
menu). For example, on dual-processors, the
limit is 90%. On four-processor computers, the
limit is 95%.
To change the CPU Usage Limit:
1 Choose Setup > Playback Engine.
2 From the CPU Usage Limit pop-up menu, select
the percentage of CPU processing you want to
allocate to Pro Tools.
3 Click OK.
Host Engine (Error Suppression)
The Host Engine option determines RTAS error
reporting during playback and recording. This is
especially useful when working with instrument
plug-ins.
You should only enable error suppression if you
are experiencing frequent RTAS errors that are
interrupting your creative workflow. When er-
ror suppression is enabled, you can experience a
degradation of audio quality. However, this may
be acceptable in order to avoid interrupting
playback and recording when working with in-
strument plug-ins. Be sure to disable error sup-
pression when you need to ensure the highest
possible audio quality, such as for a final mix.
To enable error suppression:
1 Choose Setup > Playback Engine.
2 Select Host Engine: Ignore Errors During Play-
back/Record.
3 On Mac, you can also select Minimize Additional
I/O Latency.
4 Click OK.
Error Suppression Options
Ignore Errors During Playback/Record When the
Ignore Errors During Playback/Record option is en-
abled, Pro Tools continues to play and record
even if the host processing requirements exceed
the selected CPU Usage Limit. This can result in
pops and clicks in the audio, but does not stop
the transport.
Increasing the CPU Usage Limit may slow
down screen responses on slower computers.