Difference between IDE and SCSI ??

Alan Cox alan at lxorguk.ukuu.org.uk
Mon Feb 4 11:39:55 UTC 2008

> speed in the, then, current serial circuitry.  If you could get faster,
> and accurate electronics, which you *now* can, serial can manage faster
> rates, easier and more reliably.


The reason is quite different. When you have a parallel cable all the
wires are never quite the same length, diameter or metal properties
(ditto tracks on a board). That means that the signals arrive at the ends
of each wire at different times. Your clock rate is thus limited by the
cable quality and length as well as these propogation delays. That is
what limits PATA to UDMA/133. Any faster and the bits just won't turn up
on time.

If you have one or more serial links with their own clock the clock
arrives with the data on that link as it does for example with ethernet.


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