[COFF] Daisy wheel printers (was: [TUHS] The Elements Of Style: UNIX As Literature)

[grog at lemis.com (Greg 'groggy' Lehey)]

On Tuesday, 10 November 2020 at  9:08:44 +1100, Dave Horsfall wrote:
> On Mon, 9 Nov 2020, Greg 'groggy' Lehey wrote:
>
>> The Qume printers seemed to have been the best round 1980 when we used
>> them in our applications.  In particular, a large choice of wheels and
>> fine-grained spacing.  I forget how the spacing worked.
>
> Presumably some sort of a table lookup, based on which character is about
> to be hit?  Or are you referring to the micro-spacing itself?

"Yes".  As I said, I forget.  I have a feeling that it must have been
explicit micro-spacing, since the machine didn't know anything about
the kind of daisy wheel that was fitted.

>> The golfball console for the /360 was much earlier than that, like the
>> /360 itself.  The model numbers I recall were 735, and the newer
>> generation 2731/2735.  The last digit related to the carriage width
>> (11"/15").
>
> I once had a fine collection of goofballs (as we called them); sadly lost
> in a house move :-(

I was going to say "ditto", but I think I actually sold them along
with the 735.

>> Round the time in question I bought a second-hand 735 machine.  It had
>> an arcane interface that directly talked to the magnets.  I built an
>> interface for it to a parallel port [...]
>
> I'd like to know a bit more about that interface...  You'd have to
> control the carriage, roller, swivel/tilt/hit etc.

Yes, I'm trying to recall that too.  The ball itself was controlled by
6 signals: Up 1, up 2 (for the 4 rows of characters), left 1, left 2,
left 2 (yes, twice) and right 5, for a total of 11 columns.  But my
recollection was that I only had about 10 power transistors driving
the thing.  I wish I had kept more details.  Maybe there's something
amongst the useless junk in the shed.

> How did you detect the BREAK key to get the 360's attention and
> unlock the keyboard?

I didn't.  The 735 doesn't have a BREAK key.  It was a typewriter, not
a teletype.  I used it as a printer in addition to a normal glass TTY.

Greg
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