deuna driver problems in 4.[23]

[Karl Kleinpaste]

> > On several of my deuna machines,  I get the following message
> > de0:buffer unavailable
> > This is unrelated to the load on the machine (as far as I can tell,
> > I get them on idle machines and on buisy machines).
> > ...
> > the machine becomes unable to transmit,  even though it is able to
> > receive.
> 
> We have similar problems on our 750s with 3Com boards.  Sometimes, for no
> apparent reason, the board will stop transmitting packets...
> 
> Suggestions, anyone?  I'm contemplating a sanity timer...

This is exactly what I had to do to a DEQNA (Q-bus) Ethernet board
which we use in a PDP-11/73.  When I talked with an engineer at DEC
who worked on the beast, he said it was due to a fault in a
transmitter chip which DEC uses but doesn't manufacture; it seems it
gets stuck sometimes, believing itself to be transmitting when it isn't.
A very simple sanity timer goes off every 2 seconds and asks
	if (xmit_active && current_time > xmit_start_time + <somevalue>)
			reset the board;
Or something to that effect.  DEUNAs are supposed to be similar, but
not identical, of course.

Fortunately, when resetting it like this, I don't have to re-send any
setup packets; it manages to remember that much on its own.  But
I also print a note that says something like "Enet reset" on the
console when it happens, it helps us keep track of how often the beast
gets stuck like this.  There is apparently no `real' solution, unless
you can get DEC to deal with their supplier.

The problem may be similar with the 3Coms (do DEC and 3Com have the
same supplier?  I wish I knew who they were), so the same solution should
work pretty well there, too.
-- 
Karl Kleinpaste