adams@swbatl.UUCP (745) (01/17/90)
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? And I realize this is a long shot, but if someone out there has one of these widgets they'd be willing to sell I'd sure like to add it to my collection of tube era stuff. AMD offers special thanks to the Boston Computer Museum in the ad. Is the computer museum online? -- uunet!swbatl!adams or adams@swbatl.swbt.com | Tom Adams: 314-235-7459 mail lists: uunet!swbatl!antiques-request | BOOKS WANTED: pre-1930 radio, or uunet!swbatl!antique-radio-request | electrical & scientific topics
dplatt@coherent.com (Dave Platt) (01/18/90)
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 UUCP: ...!{ames,apple,uunet}!coherent!dplatt DOMAIN: dplatt@coherent.com INTERNET: coherent!dplatt@ames.arpa, ...@uunet.uu.net USNAIL: Coherent Thought Inc. 3350 West Bayshore #205 Palo Alto CA 94303