"dougkramer" <dougkramer@...> wrote: >--- In logic-users@y..., Murray McDowall <murraymc@m...> wrote: >> -- PCI bus (32 bit wide @ 33 MHz)is 132 MByte/second >> -- Firewire is 400 Mbit per second nominally but will not deliver anything >> close to this to a firewire hard-drive -- typically tops out at 30 MByte >> per second. > >Why do firewire hard drives top out at 30 MByte/sec? >What gives with firewire being so slow? There is always a little room for confusion over bits/second and bytes/ second -- 1 byte = 8 bits so 30 Mbyte/sec = 240 mbit/sec but you seem to be clear about this distinction. 400 Mbit/second is the theoretical maximum data rate over Firewire. As to why it isn't 50Mbytes per second -- I suspect it may be something like the situation with Ethernet. As I understand it, 100 Mbit ethernet is a full duplex specification -- only about half the bandwidth is available for one way transfers. Otherwise it may simply be that there are significant overheads (extra data or waiting periods) involved in the transfer protocol which runs on Firewire. These sorts of things are pretty obvious when you are downloading a file by tcp/ip -- you can see the near continuous stream of outgoing messages from your machine back to the server that is sending the file. Regards, Murray