FireWire requires 400 or 800 AMBus card, 8-in (XLR balanced analog), 8-out (with optional D/A card), AES digital i/o (2-in, 8-out), SPDIF i/o, word clock i/o, UV22 dither, SoftLimit, channel routing. The 4 AMBus slots accept optional cards to add more i/o formats: ADAT, TDIF, Pro Tools, Pro Tools HD, SDIF-II, SSL or FiberDX.