Use of Com1

[Doug Hardie]

I have a number of servers that used to run FreeBSD 6.2.  On each of  
them the com1 port was connected via a NAS so that I could access the  
console remotely.  All worked just fine.  Then I replaced 2 of the  
servers with 2 new identical units and upgraded everything to FreeBSD  
7.0.  One of the new units works just fine.  "echo xxx > /dev/ttyd0"  
works properly and the system console can be accessed remotely.  The  
other new unit does not work.  I can't find any difference in the  
software between them.  The second one was actually made by running  
dump and restore from the first and then updating a few config files.   
The same command when run on the second machine just hangs.

My initial thoughts were the cables connecting the units were  
different.  However switching everything one at a time showed that the  
behavior was the same.  The first unit always worked with both sets of  
cables etc. and the second never did.

My next thought was that the com port itself had failed.  I have no  
direct way to verify this, but I do have another server whose hardware  
was not changed.  It was just upgraded from 6.2 to 7.0.  Its com port  
worked under 6.2, but does not under 7.0.  Hence, my third thought is  
there is some difference in a config file somewhere.  I can't find it.

The major/minor numbers are the same for the two new machine.   
Obviously the older one is different.  Getty is running on all 3 with  
"std.9600 cons25 on".  Ps shows that getty is running on all 3.   
Although I can't completely rule out hardware failure, I believe that  
there is something I have overlooked.  Any ideas what it might be or  
how to do any more diagnostic work?  Thanks.