You can rail about preservation all you want, but
11/780's were cranked
out by the hundreds of thousands and they are not the easiest system
to keep operational (as compared to a similarly-powerful desktop Microvax).
Err, I'd much rather have to keep an 11/780 running (from what I
rmemmber it's mostly TTL in there) than a microVAX (which has a number of
undocumented custom devices in it).
-tony