The following table lists the input and output capabilities of the various Avid HD audio interfaces for Avid HDX, Pro Tools|HD, and HD Native systems. Each HDX card in your system supports a maximum of 64 channels of I/O. Each Pro Tools|HD card supports a maximum of 32 channels of I/O. The HD Native card supports a maximum of 64 channels of I/O. To record and play audio with Pro Tools HD with any of these hardware configurations, you must have at least one Avid HD audio interface connected to the first port of the first card in the system.