Comparison to USB
Firewire (which started development in 1986[2]) had implementations predating USB. However USB reached industry standardisation (1994) before the IEEE-1394-1995 specification was released (1995). At this time USB 1.0 had a signaling speed of 12 and 1.5 Mbit/s (compared to 400 Mbit/s of IEEE-1394a (FireWire 400)) but cheaper implementations. Although high-speed USB 2.0 nominally runs at a higher signaling rate (480 Mbit/s) than FireWire 400, data transfers over S400 FireWire interfaces generally outperform similar transfers over USB 2.0 interfaces. Typical USB PC-hosts rarely exceed sustained transfers of 280 Mbit/s, with 240 Mbit/s being more typical. This is likely due to USB's reliance on the host-processor to manage low-level USB protocol, whereas FireWire delegates the same tasks to the interface hardware (requiring less or no CPU usage). For example, the FireWire host interface supports memory-mapped devices, which allows high-level protocols to run without loading the host CPU with interrupts and buffer-copy operations.[5] Besides throughput, other differences are that it uses simpler bus networking, provides more power over the chain, more reliable data transfer, and uses fewer CPU resources.[26]
FireWire 800 is substantially faster than Hi-Speed USB, both in theory and in practice.[27]
