On 16 Nov 2001, at 11:49, Tony Beckett wrote:

> It took 3hrs 11mins to transfer 116 Mbytes of data. I realise the
> serial ports are not fast but should it really take that long? Have
> I missed something here?

  191, call it 200 minutes for 116, call it 100 MB, or about 500 KB /
minute.  Let's call it 600 KB / minute or 10 KB / second.

  Since a byte, transmitted serially, typically takes 10 bits, this
is roughly 100 Kbps, or about twice the speed of a 56 Kbps dial-up
and close to the 115 Kbps which is the maximum supported by many
serial port hardware chips.  (Some may support 230 Kbps, but you'd
need that support on both ends to work, even if the software allows
it....)

  Okay, let's do the detail:

(116,000,000x10)/(191x60) = 1160000000/11460

  = 101221.6

or about 90% of the theoretical maximum for a common asynchronous
serial port.  LAN speeds start at about 10x that fast.

Dave Gillett

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