User guide

Chapter 6: Configuring Your Pro Tools System 45
Host Processors
The Host Processors setting determines the
number of processors in your computer allo-
cated for RTAS (Real-Time AudioSuite) plug-in
processing and other host processing tasks.
With computers that have multiple processors,
or that feature multi-core processing or hyper-
threading, this setting lets you enable multipro-
cessor support for RTAS plug-in processing and
other host processing tasks. Used in combina-
tion with the CPU Usage Limit setting, the Host
Processors setting lets you control the way RTAS
processing and other Pro Tools tasks are han-
dled by the system.
For example:
• For sessions with large numbers of RTAS plug-
ins, you can allocate 2 or more processors to
RTAS processing and set a high CPU Usage
Limit.
• For sessions with few RTAS plug-ins, you can
allocate fewer processors to RTAS processing
and set a low CPU Usage Limit to leave more
CPU resources available for automation accu-
racy, screen response, and video.
• Increase these settings to accommodate TDM
to RTAS plug-in conversion. Conversely, de-
crease these settings if you are only using
TDM plug-ins or are converting RTAS plug-ins
to TDM. TDM/RTAS conversion can be desir-
able during recording, depending on latency,
voicing needs, and record-monitoring capa-
bilities of the specific TDM and RTAS plug-ins.
• Depending on the importance of video and
overall screen response, and on the density of
automation being employed, try different
combinations of Host Processors and CPU Us-
age Limit settings to achieve the best results.
For example, to improve screen response in a
medium-sized session using a moderate num-
ber of RTAS plug-ins, try reducing the number
of RTAS plug-ins, but keep the CPU Usage Limit
set to the maximum (up to 99% on a single
processor system).
To set the number of Host Processors:
1 Choose Setup > Playback Engine.
2 From the Host Processors pop-up menu, select
the number of available processors you want to
allocate. The number of processors available var-
ies depending on how many processors are
available on your computer:
• Select 1Processor to limit host processing
for Pro Tools to one CPU in the system.
• Choose 2 Processors to enable load balanc-
ing across two available processors for
Pro Tools host processing tasks.
• On systems running four or more proces-
sors, choose the number of processors for
Pro Tools host processing tasks.
3 Click OK.
System Usage Window and Host Processing
The System Usage window (Windows > System
Usage) displays the combined amount of host
processing occurring on all enabled processors
with a single indicator, regardless of how many
processors are available in the system. If the Sys-
tem Usage Window shows that you are at the
limit of available resources, increase the number
of Host Processors and adjust the CPU Usage
Limit setting.