On Wed, Nov 8, 2017 at 8:02 PM, Noel Chiappa 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. -------------- next part -------------- An HTML attachment was scrubbed... URL: