| > | I've got a SparcStation5 and a Ultra-1E.

| mainbus0 (root): SUNW,Ultra-1

It's not a 1E.

| qec0 at sbus0 slot 0 offset 0x20000 vector 4 ipl 2: 128K memory
| qe0 at qec0 slot 0 offset 0x0 rev 1 address 08:00:20:86:a2:a0
| qe1 at qec0 slot 1 offset 0x0 rev 1 address 08:00:20:86:a2:a0
| qe2 at qec0 slot 2 offset 0x0 rev 1 address 08:00:20:86:a2:a0
| qe at qec0 slot 3 offset 0x0 not configured

Can you live with just 3 out of the 4?

The first thing we need to do to get this fixed is figure out
exactly where the hang occurs, which means either adding a
bunch of printf() to the driver, or opening up the case and
hitting the XIR pin (which is inconveniently located under
the cgsix) once the machine hangs.

If you want to file a PR, go ahead.  But it's unlikely to
be fixed without access to the proper hardware.

Eduardo