[TUHS] pre-more pager?

[clemc@ccc.com (Clem Cole)]

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On Wed, Nov 8, 2017 at 8:02 PM, Noel Chiappa <jnc at mercury.lcs.mit.edu>
wrote:

> If one were using a serial line
> hooked up to a DZ (and those were common - DH's were _much_ more
> expensive, so
> poor places like my lab at MIT used DZ's), then _every character printed_
> caused an interrupt.


​Right, although many (most) Unix sites used Able DHDM's which were cheaper
than DEC DZ's, took less space in the backplane, had full modem control
(inc RTS/CTS handshaking in HW) and were DMA.   But, my memory is that they
did not show up until '78 though.

The truth is DZ sucked from a performance standpoint. Besides not being
able to support RTS/CTS flow control, the 8 serial ports shared an input
buffer in the HW IIRC and the UART only had 2 chars of buffering.    An
8-port DZ with all lines running 19.2K baud could kill a 780.    People
that ran the "Berk-net" (which a pre-TCP networking system for UNIX that
ran on serial lines) needed spread out the Berk-Net load between different
DZ lines.  No so if you have Able gear.

So I'll take the 'common' note to be if you used a 'pure DEC' set up - you
used DZ-11s.  ​  But as you said most of us were looking at costs, so
'foreign' peripherals were also 'common' in the UNIX community.  DH11's
were preferred.
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