Setup Guide

003 Family Setup Guide22
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 RTAS 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
specify for RTAS processing. This value can
range from 85% for single-processor computers,
and 99% for multiprocessor computers (which
dedicate 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 RTAS 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.
RTAS Engine (RTAS Error Suppression)
The RTAS Engine options determine RTAS error
reporting during playback and recording. This is
especially useful when working with instrument
plug-ins.
You should only enable RTAS error suppression
if you are experiencing frequent RTAS errors
that are interrupting your creative workflow.
When RTAS error 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 instrument plug-ins. Be sure
to disable RTAS error suppression when you
need to ensure the highest possible audio qual-
ity, such as for a final mix.
To enable RTAS error suppression:
1 Choose Setup > Playback Engine.
2 Select Ignore Errors During Playback/Record.
3 If available, you can also select Minimize Addi-
tional I/O Latency.
4 Click OK.
RTAS Error Suppression Options
Ignore Errors During Playback/Record When en-
abled, Pro Tools continues to play and record
even if the RTAS processing requirements ex-
ceed the selected CPU Usage Limit. This can result
in pops and clicks in the audio, but does not
stop the transport.
Minimize Additional I/O Latency (Mac
Only) When enabled, any additional latency due
to suppressing RTAS errors during playback and
record is minimized to 128 samples. Suppressing
RTAS errors requires at least 128 samples of ad-
ditional buffering on some systems. If this op-
tion is disabled, the buffer is half the H/W Buffer
Increasing the CPU Usage Limit may slow
down screen responses on slower computers.