Reading ancient paper digital media (was Re: Hamurabi Focal source)
csquared3 at tx.rr.com
Sun Apr 4 01:29:54 CDT 2010
Fred Cisin wrote:
> On Thu, 1 Apr 2010, Chuck Guzis wrote:
>> What was the proportion of readers that read colum-serial versus row-
>> serial? I believe the CDC 415 punch had its read station as 80
>> brushes, reading the card just punched row-wise.
> It is it character based device or a record device?
> 026, 029, etc. would obviously read a column at a time (12 brushes).
> 084, etc. would read a row at a time, even though they were only
> reading one column (one brush).
Errrmm, I never worked on an 029 but I'm reasonably sure the 026 has no
"brushes" at all. ISTR the read station worked by trying to penetrate
the card with some little lightly spring loaded pins. Where there were
holes the penetration succeeded and contacts closed (or maybe opened).
In unpunched areas the opposite happened. I must admit that it amounts
to the same thing. I also seem to recall the 084 used a 1-column
optical sensor. Its predecessors back through the 080 (and probably
earlier) did use a single brush however. Again, same effect, just a
different physical implementation. I do remember the 084 was one more
screaming fast card sorter; I rather suspect that brush bounce etc. was
just too much to cope with to achieve reliable operation at that speed.
I'm trying unsuccessfully to remember just what the read rate was for
the 084. Anyone remember?
> But, if there would be no processing of the data until it was all read,
> obviously 80 brushes and a short path would be faster than 12 brushes and
> a long path.
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