[ntp:hackers] Serial port jitter in FreeBSD

Poul-Henning Kamp phk at phk.freebsd.dk
Thu Oct 27 03:32:34 PDT 2005


In message <20051026165438.BBF8CBDD1 at ip-64-139-1-69.sjc.megapath.net>, Hal Murr
ay writes:
>
>> 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.

# man 4 sio
[...]

           In /boot/device.hints:
           hint.sio.0.at="isa"
           hint.sio.0.port="0x3f8"
           hint.sio.0.flags="0x10"
           hint.sio.0.irq="4"
           hint.sio.1.at="isa"
           hint.sio.1.port="0x2f8"
           hint.sio.1.flags="0x0"
           hint.sio.1.irq="3"

[...]

     Meaning of flags:
           0x00001   shared IRQs
           0x00002   disable FIFO
[...]

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.


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