Specifications

Chapter 6: System Setup 67
To change the Hardware Buffer Size:
1 Choose Setup > Playback Engine.
2 From the H/W Buffer Size pop-up menu, select
the audio buffer size, in samples.
3 Click OK.
Host Processors
The Host Processors setting in the Playback En-
gine determines the number of processors in your
computer allocated for Native (AAX and RTAS)
plug-in processing and other host processing tasks.
With computers that have multiple processors, or
that feature multi-core processing or hyperthread-
ing, this setting lets you enable multiprocessor
support for host processing tasks. Used in combi-
nation with the
CPU Usage Limit setting, the Host
Processors
setting lets you control the way host-
processing tasks are handled by the system.
For example:
• For sessions with large numbers of Native plug-
ins, you can allocate 2 or more processors to Na-
tive processing and set a high
CPU Usage Limit.
• For sessions with few Native plug-ins, you can
allocate fewer processors to host-based process-
ing 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 DSP-to-
Native plug-in conversion. Conversely, decrease
these settings if you are only using DSP plug-ins
or are converting Native plug-ins to DSP. DSP-
to-Native conversion can be desirable during re-
cording, depending on latency, voicing needs,
and record-monitoring capabilities of the spe-
cific DSP and Native plug-ins.
• Depending on the importance of video and over-
all screen response, and on the density of auto-
mation being employed, try different
combinations of
Host Processors and CPU
Usage Limit
settings to achieve the best results.
For example, to improve screen response in a
medium-sized session using a moderate number
of Native plug-ins, try reducing the number of
Native plug-ins, but keep the
CPU Usage Limit
set to the maximum (up to 99% on a single-pro-
cessor 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 available processors
depends on your computer:
• Select
1 Processor to limit host processing for
Pro Tools to one CPU in the system.
• Choose
2 Processors to enable load balancing
across two available processors for Pro Tools
host processing tasks.
• On systems running four or more processors,
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 pro-
cessing occurring on all enabled processors with a
single indicator, regardless of how many proces-
sors are available in the system. If the System Us-
age Window shows that you are at the limit of
available resources, increase the number of
Host
Processors
and adjust the CPU Usage Limit set-
ting. (For more information, see “System Usage”
on page 85.)