New Serial Problems (was Re: [Soekris] gotcha with the net4501 clock)

phk@phk.freebsd.dk phk at phk.freebsd.dk
Fri Feb 14 08:00:23 UTC 2003


In message <4D297825-3F6B-11D7-9565-000393BB56F2 at WarningSystems.com>, David Kel

>Very interesting because "me too, the older 4501's work better." While 
>I "knew" the main crystal wasn't part of the problem, it was the only 
>visible difference between the working units and randomly failing 
>units. All the failing units had 33.3333 MHz main crystals. We tried 
>swapping a 32.768 MHz crystal from a working unit and the problem 
>stayed with the PCB. So its not some oddball thing happening in the 
>scheduler.

The serial port is clocked from the 32.768 kHz "cmos" crystal.  If
the PLL which runs the frequency up is unstable, the serial port
would suffer, but I doubt that is the problem.

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