🚀 go-pugleaf

In article <1113@swbatl.UUCP> adams@swbatl.UUCP (Tom Adams - 235-745) writes:
> Amd has an ad for their CMOS EPROMS in EE Times (1/15 pp 6) that mentions
> several historical memory devices.  One that cought my eye, is a
> Selectron Tube that had "random  access to 256 bits of storage with
> a cycle time of a mere 20 ms."  Anyone heard of these before?  Or
> know the typical applications?

Hee hee.  Story time!  I heard this years ago, so I probably have some
of the details wrong... but I think the following is largely accurate...

Quite a few years ago (in terms of the computer industry), tubes such
as this were used as the primary storage medium on the original "Von
Neumann Stored Program Computer" (that's the term I've heard;  it may
not be accurate).  The bits were stored on an energized phosphor
coating at one end of the tube, and were written and read by an
electron beam.  The famous Tektronix storage-tube graphics terminals
(4010 et al) used a similar mechanism.

The tubes on the Von Neumann machine tended to suffer from some aging
(just as the Tektronics storage-scopes do).  The phosphor would "burn"
from the impact of the electron beam, and would eventually degrade enough
that bits couldn't be stored reliably.  The tubes would then require
replacement.

On the Von Neumann machine, the tubes were mounted in a large rack panel
of some sort, with the phosphor-end facing out into the room.  It was
actually possible to see the bits flicker on and off!  An experienced
technician could often tell which tubes were approaching the end of their
useful lifetime, by visually checking the brightness of the bits.

During the regular PM periods, the folks responsible for servicing the
machine would boot up a special diagnostic program, which would run
ripple patterns and other such useful logic-testing sequences through
the main memory.  This produced a very pretty arcade-like display across
the face of the storage-tube cabinet.

One of the people using the Von Neumann machine was a certain Ivan
Sutherland... the developer of Sketchpad (the first-ever graphics
tablet), co-founder of Evans & Sutherland, and the recent Turing Award
recipient.  I believe Ivan was a grad-student at the time.  Anyhow,
Ivan wrote up a new program for the machine, and then substituted it
for the hardware-diagnostic program deck.

A few days later, the machine was taken down for PM.  The technician booted
the "diagnostic", and the machine immediately hard-halted.  The technician
reset the machine, and tried again... same result.

Suspecting a serious fault in the memory logic, the technician opened up
the storage-tube cabinet...

... and there, staring out at him in a cheery display of lit and unlit
bits, was an unprintable four-letter word!

Shortly thereafter, a stern memo was circulated around the lab, stating
that it was NOT permissible to snitch the diagnostic programs and
substitute new ones in their place.
-- 
Dave Platt                                             VOICE: (415) 493-8805
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