[Gllug] re: SCSI vs SATA

[Christopher Hunter]

On Thursday 10 Jun 2004 12:39 pm, Richard Jones wrote:

> Yes, I used to do this sort of stuff.  Once you start hitting 100s of
> MHz or GHz speed, all the traces need to be the same length, each
> signal needs a separate return path, you need a huge ground plane, and
> you need to add resistors to the end of each signal to stop
> reflections.  The resistors were a particular problem I seem to
> remember - we actually had to build the boards, and measure the
> signals with an oscilloscope to find the right size of resistor.  This
> was nearly 10 years ago, I don't know if things have improved since.

No it hasn't!

> There is software which can do the layout semi-automatically but it's
> very expensive, takes a long long time to run, and requires manual
> intervention.  And it doesn't really do the specialist stuff anyway
> (eg. we always used to lay out clock traces by hand before letting the
> software have a go at the rest).

I've yet to find an autorouter that can do the job a tenth as well as me!  
However, I do use software tools for the draughting, though I generally 
sketch an approximate layout by hand (pencil on paper) before I start.

Chris

-- 
Gllug mailing list  -  Gllug at gllug.org.uk
http://lists.gllug.org.uk/mailman/listinfo/gllug