29 May
2018
29 May
'18
7:12 a.m.
On Mon, 28 May 2018, Paul Winalski wrote:
DZ11s were available on PDP-11s and VAXen as well as
the KS10. Because
the controller had no buffer it was dirt cheap. OK, perhaps, for a
realtime or lab application, but if you were doing timesharing it could
bring the CPU to its knees in short order. Some idiot decided to use
the same idea (no buffer in the controller) to reduce the cost of the
TU58 (aka DECtape II), Unlike the original DECtape, which was extremely
reliable, the TU58 was prone to frequent data overrun and underrun
errors even if you set things up such that it got top scheduler
priority.
Odd; I have a clear recollection that UNSW's driver (or was it Basser?)
did not use interrupts (too slow, as you point out) but used the clock
interrupt to empty the silos every so often. I'd check the source in the
Unix Archive, but I don't remember which disk image it's in; what I do
remember was that it went like a bat out of hell, and Elec Eng had
something like eight of them on their 11/70.
Can anyone confirm or deny this?
We also had a DZ-11 on our 11/60 (and the 11/40 before that), and it
worked OK, keeping the DJ-11 company.
-- Dave, possibly suffering from mental bit-rot