An OutoftheMain Activity 3789
Charles Richmond There are two separate issues here, which should not (imho) be conflated: namely DIY computing, and Z80s. There were other ways to roll your own. As I recall (& I...
at the university in the late 60s, we had 2702 telecommunication controller with type-I line-scanner (2741) and type-III line-scanner (1052). the university got was TTY-33 machines and had to get a type-II line-scanner (TTY). The type-II line-scanner upgrade for the 2702 arrived in a box that said Heathkit (obviously they were building other things).
It was the same in Australia a little earlier. Late 60's, early 70's The only modem you could lease was Swedish. I was a brat working for Reuters AAP then. The...
the 2702 had "SAD" command that you specified for each line ... which buttociated a specific line-scanner with a specific line-port.
original cp67 delivered to the university had 2741 (type-1 line-scanner) and 1052 (type-III line scanner) terminal support. It had some magic code that would do a sequence of operations with different line-scanner combinations in order to dynamically determine the terminal type.
with the addition of type-II line-scanner and TTYs ... I had to add TTY support to cp67. I tried to emulate the same magic code as had been done for 2741 & 1052. It work ok with fixed line terminals ... however, I wanted to also do it for dialed terminals. The support seemed to almost work ... i.e. use the same (common phone number) dialed port-line for all terminals. the gotcha was that the line speed oscillator was hard wired to each line ... while it was possible to dynamically change the line-scanner on a port-line basis ... it wasn't actually possible to dynamically change the line-port baud rate (defeating the ability to actually use a common phone number of all terminal types).
this was sort of the motivation for the university to start a project to build our own telecommunication controller. somebody wrote an article blaiming four of use for spawning the plug-compatible (clone) controller business.
project involved reverse engineering the mainframe channel interface and building a channel interface card for an interdata-3 ... and progrmaming the interdata-3 to emulate the mainframe telecommunication controller. one of the features added-programmed for the interdata-3 was to dynamically determine port-line-terminal baud rate.
I Barb then replied: As others have said, the BSDs were available in the early 1990s despite the copyright battle...
misc. other posts mentioning clone controller:
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