Sun 2/120 keyboard and mouse?

[Pete Turnbull]

On Mar 19 2005, 23:43, Jules Richardson wrote:

> We couldn't get it to work with any transceiver we tried (SQE test
was
> off, FWIW), whether hooked up to a hub or not - it still gave a
> complaint about heartbeat at startup and then subsequent "no carrier"
> errors (and the "Ethernet jammed" errors).

The complaint about "heartbeat" is because the interface is expecting
to see the SQE test appear a few bit times after the end of the frame.

"Ethernet jammed" might mean it's seeing a continuous jam signal, or at
least sees a jam signal when it listens to the wire to see if it can
transmit.  A jam signal is what a repeater puts on the wire when it
detects a collision (and it would see the SQE test signal as a
collision).  It's an alternating set of 1s and 0s that lasts 96 bit
times, as I recall (an ordinary station can also generate a jam signal
but not such a long one), and the object of that is to force everything
to see a collision and back off.  Now it so happens that 96 bit times
is also the interframe gap length, so if you have a repeater with a
transceiver set to do SQE tests, it sends an SQE test starting a few
bit times into the IFG, then generates a jam which will still be there
slightly after the end of the IFG, just when the station might be
checking for carrier again.  Have you got another repeater somewhere
with a transceiver on it?  Or are you missing a terminator so that the
voltage is out of spec and might look like a collision?

> As said in a private mail just now though, we'd had this problem with
> our PDP 11/84 - on the advice of an ex-DEC chap, it'd only talk to
one
> of these DEC units rather than any kind of AUI-equipped hub (or a
> transceiver). On a whim we tried the same with the Sun, and it seems
to
> have improved matters.

I've had various DEC machines, like my 11/83, attached to both
thickwire and thinwire with non-DEC transceivers and never had a
problem.  I do check the SQE test, though :-)

-- 
Pete						Peter Turnbull
						Network Manager
						University of York