Realistically, the 1394 interconnect is the only viable solution for the scenario we've just reviewed. The reasons include bandwidth, topology, isochronous capability, timing information carried with the data, and peer-to-peer communications. It's also important that 1394 allows scalability via additional devices that musicians can add to the bus as required.
Professional audio requires significant bandwidth. The I/O boxes capture 24-bit data sampled at rates as fast as 96 kHz. The 1394 interconnect supports data rates as fast as 400 or 800 Mbps. And faster 1.6- and 3.2-Gbps versions are on the way. Generally, the 400-Mbps flavor affords the performance required in a professional audio application.
The story, however, goes well beyond bandwidth. The 1394 interconnect is inherently a peer-to-peer bus. Any device can initiate a data transfer to any other device or to multiple devices. The host PC does not have to be involved. In our concert scenario, the I/O box can transfer data directly to a mixer and the PC.
The 1394 interconnect guarantees QoS (quality of service) via its isochronous capabilities. Essentially, a 1394-based device can reserve the bandwidth it needs. Ad hoc traffic on the interconnect will not impact the real-time audio streams.
Timing information is also carried along with data on the 1394 interface. That timing information is critical for the producers mixing a recording back in the studio - allowing easy synchronization of multiple channels.
The scalability angle allows musicians to buy I/O boxes and mixers with the channels they presently require while knowing that they may need more channels later. It may also allow a band to carry less gear to a performance relative to what they need in a studio.
The 1394 interconnect supports almost any topology including most commonly a daisy chain of devices. That makes it easy to connect a PC, I/O box, and mixer. But device manufacturers such as Presonus also utilize that topology to offer an expandable system. For example, you can link two 16-channel mixers and realize a 32-channel mixer with the 1394 interface proving the real-time connection.
The peer-to-peer and synchronization capabilities also come into play in such daisy-chained scenarios. For example, the second mixer acts as a slave to the first. But the slave mixer can simultaneously transfer its output to the master mixer and the PC.