[TUHS] Control-T (was top)

Dave Horsfall dave at horsfall.org
Tue May 29 11:12:09 AEST 2018

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

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