[Park Seward]

512 RAM is the minimum Pro Tools can use. Adding more RAM will improve things greatly.

Total System RAM
512MB minimum required for Pro Tools LE 7.0/7.1 (Digi 002, 002 Rack, Mbox 2, Mbox 2 Mini, Mbox) - More Recommended
768MB minimum required for Pro Tools LE 7.1.2 (Mbox 2 Pro) - More Recommended
More RAM increases overall system and Pro Tools performance
More RAM suggested for sessions with high edit density, extensive use of plug-ins, or simultaneous use with MIDI sequencers

Low Buffer Size/Multi-Processor Issues with Pro Tools 7 on Mac OS X


There is a known issue with low hardware buffer sizes and the multiprocessor RTAS engine of Pro Tools 7 (HD, LE, and M-Powered). Specifically at buffer sizes lower than 512, multiprocessor setups of Pro Tools can show a marked INCREASE in CPU utilization as you enable more processors. While dual processor models also exhibit this behavior somewhat, it is more noticeable with 3 or 4 processors enabled on the Power Mac Quad G5.

Digidesign is aware of the problem, and is actively working on the issue. We have run a number of tests, and while we continue to investigate a fix, our tests have turned up a few situations where this problem is likely to manifest, and a workaround for those scenarios.

At buffer sizes 512 and higher, we recommend you use the maximum number of processors. More processors will give you more cycles to run additional RTAS plug-ins and more tracks with little additional overhead from Pro Tools' management of additional processors.

We recommend the following setting for existing or new sessions that require lower buffer sizes:
In "Setup/Playback Engine" lower "RTAS Processors" to "2 Processors".
If you still see errors, one or more of the following will reduce the CPU utilization below the error threshold:
- Make some plug-ins inactive
- Make some tracks inactive
If errors still occur, follow the same instructions with one processor enabled
Once you are mixing, you may use all processors, and restore any inactive tracks/plug-ins. You can then increase the HW buffer size to 512 or higher to prevent errors.

Try updating to 7.1.