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

David Kelly dkelly at
Mon Feb 17 18:42:43 UTC 2003

On Thursday, February 13, 2003, at 09:53 AM, David Kelly wrote:
> On Thursday, February 13, 2003, at 12:41 AM, Manuel Kasper wrote:
>>> We have 20 or 30 Soekris 4501's running a FreeBSD 4.4 kernel and are
>>> having a problem with some boards in transmitting a simple 12 byte
>>> burst at 300 baud. The 2nd character is replicated in the 3rd 
>>> position.
>>> The count is still 12. Is random on some 4501's, and never on others
>>> while running the exact same (not even copy of) CF card.
>> Just my $0.02:
>> I'm seeing this, too, on a newer net4501 (which says net45xx in the 
>> BIOS)
>> - characters are duplicated at random in the output from FreeBSD 4.7, 
>> and
>> while the loader is loading the kernel and displaying the swoosh (/ - 
>> \
>> ....) it stops several times for about 4 seconds (at random). Once the
>> kernel is loaded, it doesn't stop anymore, but characters are still
>> duplicated every now and then. Annoying, but except for this, it's 
>> working
>> perfectly.

Ironic in that today we demonstrated the problem did not occur at 1200 
baud. Only at 300. Disabling the 16550 FIFO appears to band-aid the 
problem. If we really needed the FIFO, I'd play with different depths. 
But only need to send 12 bytes every now and then so I'm not terribly 
worried about not having a FIFO.

For FreeBSD put this in /boot/device.hints or similar in the kernel 
config file:


("0x10" is the default)

David Kelly N4HHE, dkelly at, (256) 704-8774 x105
Whom computers would destroy, they must first drive mad.

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