[ntp:hackers] Serial port jitter in FreeBSD

Hal Murray hmurray at suespammers.org
Wed Oct 26 09:54:37 PDT 2005

> The serial port jitter with refclocks and FreeBSD rackety and mort is
> rather huge. I have a vague recollection of what can be done about
> that,  specifically to diable the UART FIFO and software queue in the
> driver.  I've done that for most of the systems here, but haven't a
> clue how to  do that with FreeBSD and various motherboards. I've
> surfed  www.freebsd.org with no joy. Help? 

Seems like a good topic for the Wiki.

I'd like a clean recipe for disabling the FIFO on a Linux box.

setserial has a low_latency option, but I couldn't get it to do anything.  
John Ackermann has graphs showing that it worked for him.  ???

I gave up and hacked the kernel - one line of code in the right place.

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