[Gllug] re: SCSI vs SATA

Chris Bell chrisbell at overview.demon.co.uk
Thu Jun 10 13:14:45 UTC 2004


On Thu 10 Jun, Christian Smith wrote:
> 
> On Thu, 10 Jun 2004, Tom Fairbairn wrote:
> 
> >
> >
> >>the necessary chippery is easily (and quite cheaply) available
> >
> >So is Linux, but that doesn't mean it isn't complicated!  What I meant by that
> >comment was that the serial stuff is far more complicated as compared to what
> >you need for parallel.
> 
> 
> Until you have to route all those parallel tracks so that they're all the
> same length. I'm no PCB designer, but I guess a small number of very high
> speed tracks are easier to lay out than loads of high speed tracks, hence
> the move to 16 bit buses in RDRAM and HyperTransport.
> 
> Against the costs of everyone routing PCBs correctly, the one time cost of
> designing more complicated serial drivers is probably low.
> 
   But we are talking about real-time data, there is no time available for
each chip to do its own serial/parallel conversions. Signals flying around
the board are not nice clean pulses at the best of times, they can originate
at many points along a track with sometimes multiple destinations, but as
long as they appear to be on the correct side of the trigger level(s) as the
clock edge arrives then it all works OK.


-- 
Chris Bell

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