[wellylug] [OT] Internet & Citylink

Leo pizbit at neko.net.nz
Mon Feb 28 20:37:24 NZDT 2005


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Richard Hector wrote:
| On Mon, Feb 28, 2005 at 07:59:50PM +1300, Jamie Dobbs wrote:
|
|>David Antliff wrote:
|>
|>
|>>On Mon, 28 Feb 2005, Cliff Pratt wrote:
|>>
|>>
|>>>The rule of thumb used to be to divide by 10. That was to allow for
|>>>the overhead of stop and start bits. I guess that only applies to
|>>>serial port lines. I also guess that it doesn't apply to ADSL, but
|>>>I'm not sure why. Anyone care to comment?
|>>
|>>
|>>Because on broadband services the overhead is transparent to the user?
|>>The advertised speed is customer payload rate, not connection speed or
|>>symbol rate or anything like that. So a 256kbps link is 256 * 1000 (a
|>>kilobit is 1000 bits, not 1024) which is 256000/8 = 32000 Bps or
|>>31.25KB/sec.
|>>
|>
|>1000 bits is NOT a kilobit (or at least wasn't when I went to either
|>University or Polytech, or in the 25 years I've been using computers).
|>The numeric base of computers is powers of 2, and you cannot get 1000
|>from a whole power of 2, the closest you can get is 1024 which is the
|>correct definition of kilo in computer terms.
|
|
| The data comms people have usually stuck to real prefixes rather than
| the weird ones computer people use.
|
| Adopting existing terms for the 1024 multiples was a silly thing to do,
| IMHO.
|
| Richard
|
|
Just to clear things up: http://physics.nist.gov/cuu/Units/binary.html
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