1 Apr
2010
1 Apr
'10
11:18 a.m.
----------------Original Message:
Date: Thu, 01 Apr 2010 08:02:31 -0700
From: "Chuck Guzis" <cclist at sydex.com>
Subject: RE: Reading ancient paper digital media (was Re: Hamurabi
Focal source)
On 1 Apr 2010 at 0:17, Ian King wrote:
Interestingly, the idea of a timing mechanism hosted
on the medium
itself never occurred to Herman Hollerith or his successors, which I
guess speaks to their confidence in their engineering.
Not necessarily. If you look at Hollerith's card reader, it read the
entire card in parallel, using spring-loaded probes that would extend
through the card holes and touch a pool of mercury. No need for
clocking.
Serial card reading came later when the card was not manually read.
If you're going to automate card transport, then reading the card
serially actually is easier.
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.
--Chuck
--------------------Reply:
As a matter of fact reading the card 'sideways' was a basic principle
of the electro-mechanical punched card systems that (along with
card sales) were IBM's bread and butter until the mid-sixties.
With the exception of keypunches, paper tape converters etc. these
machines were 'clocked' through the 12 states (12,11,0-9); the (firmly
clamped) cards and various gears, relays, punches, type bars, etc.
were cycled through these 12 states in synchronized parallel unison,
much like most of the manual 'posting machines' with full row and
column keyboards that preceded and coexisted with them.
Timing diagrams looked much like the diagrams we're familiar with,
but they were usually calibrated in degrees of rotation of the master
camshaft instead of time.
Interesting to compare not only the architectures of then vs. now,
but the overall systems; a room full of various machines would be
more or less the equivalent of a fairly simple micro, each machine
(and operator in some cases) would be a programming algorithm
or an IC, the data path would be an actual real well-worn path where
cards would be carried from one machine to the next in the processing
sequence, patch boards would be EPROMs, etc. etc.
The hardware and documentation may be preserved, but I suspect
the design of the actual application systems, i.e. 'programs' where
procedures are in fact different physical machines, is becoming a
lost art.