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Date: Sat, 15 Mar 1997 02:50:29 +1100
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199703141550.CAA31096@godzilla.zeta.org.au>
To: ahd@kew.com, bde@zeta.org.au, j@uriah.heep.sax.de
Subject: Re: i386/2984: serial console speed goes to hell during boot
Cc: freebsd-bugs@freefall.freebsd.org
Sender: owner-bugs@FreeBSD.ORG
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>>  >	When booting the 2.2 GAMMA release using a serial console
>>  >	the output (to an IBM PS/1 previously successfully used
>>  >	for a serial console for 2.1.5-RELEASE for another 386),
>>  >	output is normal 9600 bps output until about the time the
>>  >	NPU is detected.  Then, output slows to a crawl (~ 1
>>  >	character/second) until shutdown ... the last two lines
>>  >	before reboot are printed at a normal speed (again), implying
>>  >	the hardware is (still) fine.
>>  
>>  Check that nothing in /etc/rc.serial touches the console port.
>
>But rc.serial is run towards the end of /etc/rc, not right after the
>npx probe?

Output interrupts must be broken.  They may have always been broken,
but 2.1.5 polls for lost ones every 10 msec, so output goes out at at
least 100 cps, while 2.2 polls every second, so output goes out at at
least 1 cps.  You can restore the 2.1.5 polling frequency by setting
the flag to recover sooner from lost output interrupts, or by not
using interrupts at all.  See the sio man page.

Bruce