The Host Processors setting in the Playback Engine 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 hyperthreading, this setting lets you enable multiprocessor support for host processing tasks. Used in combination with the CPU Usage Limit setting, the Host Processors setting lets you control the way host-processing tasks are handled by the system.
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For sessions with large numbers of Native plug-ins, you can allocate 2 or more processors to Native processing and set a high CPU Usage Limit.
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For sessions with few Native plug-ins, you can allocate fewer processors to host-based processing and set a low CPU Usage Limit to leave more CPU resources available for automation accuracy, screen response, and video.
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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 recording, depending on latency, voicing needs, and record-monitoring capabilities of the specific DSP and Native plug-ins.
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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 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-processor system).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:
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Choose 2 Processors to enable load balancing across two available processors for Pro Tools host processing tasks.
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On systems running four or more processors, choose the number of processors for Pro Tools host processing tasks.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 System 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. (For more information, see System Usage.)