User Manual

003 & 003 Rack Getting Started Guide26
CPU Usage Limit
The CPU Usage Limit controls the percentage of
CPU resources allocated to Pro Tools host pro-
cessing 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 ef-
fect of Pro Tools processing on other CPU-inten-
sive tasks, such as screen redraws, and are useful
when you are experiencing slow system re-
sponse, 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 real-time 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 percent for single-processor computers
to 99 percent for multi-processor computers.
To change the CPU Usage Limit:
1 Choose Setup > Playback Engine.
2 From the CPU Usage Limit pop-up menu, se-
lect 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.
There are two RTAS Engine 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 re-
sult in pops and clicks in the audio, as well as ad-
ditional latency, but does not stop the transport.
This will only suppress errors in the RTAS en-
gine. Disk-based errors (if any) will continue to
stop the transport.
Minimize Additional I/O Latency (Mac OS X
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
Size, or at least 128 samples (which ever is
greater). If you are on a slower computer, you
may not want to enable this option since doing
so can adversely affect performance.
Increasing the CPU Usage Limit may slow
down screen response on slower computers.