Re: gEDA-user: terminators

[DJ Delorie <dj@xxxxxxxxxxx>]

> Hey Steven, that's a pretty interesting analysis.  I just want to add 
> something from Dr. Howard Johnson's book on this stuff.  His claim is 
> that you can treat a pcb trace as a lumped system if the trace is less 
> than 1/4 * 'length of the edge'.  Well, at 170 ps/inch the length of the 
> edge is about 5.8" - that's exactly 1/2 your result.

If I remove the LA connector and shove the sdram closer to the fpga, I
get a trace length range of 2027 mils (CLK) down to 281 mils (DQ7), a
mis-match of 1.7 inches, or just under 1/3 of 5.8".

I wonder if I could drive the shorter traces less than the longer
ones, to match up the edges at the sdram?


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