“I’m running an Mbox with Pro Tools LE on a 867 MHz G4 and getting an error that says “Computer usage holding off USB” and then offers some suggestions such as deleting tracks and removing plug-ins. My friend has similar problems on his PowerBook. Is this common? What can I do to fix it?”
Giving attention to USB is pretty low on the Mac’s list of priorities so when your computer is working hard at other things it is possible to get this error. It’s actually pretty rare on newer Macs, but since there are a number of possible causes it depends on your particular setup. The Mbox is a new product and we expect Digidesign will continue to work to minimize the occurrence of this error on all types of systems, whether that’s with new drivers, firmware updates or updates to the Pro Tools LE application. Meanwhile there are some things you can do to improve your success.
First, make sure your Mbox is connected directly to the computer, not running through any type of hub. In general you should make sure you’ve followed the setup instructions that came with your Mbox to the letter. Feel free to modify things later, once your system is running smoothly, but when having problems the conservative approach is always best to eliminate variables.
As the error message indicates you can reduce the number of tracks or plug-ins. That doesn’t mean you have to uninstall plug-ins, it’s just referring to having less plug-ins instantiated or active on the particular session. Sometimes neither of these methods is a very attractive option so read on for more ideas.
General tricks to increase the performance of your Mac (and thus Pro Tools in this case) include disabling non-critical extensions (using the Extension Manager Control Panel), increasing the RAM allocated to the application, which in this case would be both Pro Tools and DAE (DAE is found in your system folder), don’t have other applications running in the background, and getting higher performance hard drives (which could be a whole Tech Tip in and of itself). To try out your system with minimal extensions running, just open Extensions Manager and select the base set for your OS. Make a copy of it with a new name, and then turn on the five or six Digidesign extensions and the one OMS extension. If this helps you can then turn on other stuff from there until you notice performance decreasing. Some users have also noticed improvement by turning off all the networking extensions.
If you haven’t done so already, upgrade your Mac’s OS to 9.2.2. This version definitely works better than previous versions.
Under the hardware setup menu in Pro Tools, increase the size of your sample buffer. This will increase latency, but when you’re ready for mixing and need the extra processing required for mixing, latency generally isn’t an issue. According to Digidesign you can also lower the maximum CPU usage for Pro Tools in this same menu, but generally we haven’t seen this make much of a difference on higher performance machines such as your 867.
On PowerBooks you have to make sure you disable all the sleep and screen saver functions (not a bad idea for desktop machines either), and be sure you don’t have processor cycling enabled.
And finally, one that Digi doesn’t appear to have documented anywhere, be careful on machines with dual monitor setups. There seems to be some type of conflict with some video cards such that having a Pro Tools window open on each of the monitors can cause this error (no matter how stripped down the Mac is otherwise). If you’re having this problem you don’t have to disable the second monitor, just make sure all the Pro Tools windows are only displayed on the main monitor.