Interconnecting classic computers

Jim Battle frustum at
Mon May 5 20:30:02 CDT 2008

Eric Smith wrote:
> Fred wrote:
>> If we are going to discuss the WORST systems, surely we can't leave out
>> the TRS80 casstte port system that RS came up with for classrooms!
> Well, don't leave us in suspense.  In what way was it done badly?
> Was it unreliable?  Did it fail to meet its design objectives?

Our school system had one, back in 1981.

There was a panel that was a mux/demux to 24-ish diskless model 3s.  The 
cassette in/out from each of these came to the mux/demux box, through a 
selector switch, to the teachers model 3 w/dual floppy system.

At the start of a lesson, the teacher would tell the students, OK, type 

The teacher would load the lesson program into memory, then type "CSAVE" 
to broadcast it to all the listening machines.  I believe it was 
bidirectional.  To upload, the teacher would select one of the 24 
machines to listen to and the CLOAD/CSAVE was swapped.

OK, so it depends on the notoriously unreliable TRS-80 cassette 
interface, and on the cooperation of 24 clueless sixteen year olds. 
What could possibly go wrong?

Truthfully, it was probably more reliable than CSAVE/CLOAD with a 
cassette since there was no gain/bias/speed variation to contend with, 
and it was probably about the cheapest solution to the problem.

As a side note, I had learned to program on BASIC on the school's wang 
2200 computers, then I started programming in assembly on the TRS-80s 
that were available.  The summer before my senior year the high school 
placed an ad looking for people to write educational programs for the 50 
or so model 3s they had just bought.  At the time there wasn't a lot of 
off the shelf software for what they wanted, so they wrote it 
themselves.  They were paying $10/hr, much more than the $5/hr I was 
getting paid to program Apple IIs.  I applied and got rejected, and I 
heard they hired a number of college-level CS majors.

At the start of the following school year I had to do a couple weeks (1 
hr/day) of "Computer Orientation", which all the teachers and students 
had to go through.  There were some lessons on how to type, how to load 
a program, and the very rudiments of programming in BASIC.  I looked at 
the source code of the programs they had developed and saw that the 
college CS majors weren't any more qualified than me (often less) to 
write those programs.  I was even more shocked when I later read that 
the $200K the school had spent on the computers and software development 
were more than defrayed when they sold the rights to their software to 
some publishing house for more than $200K.

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