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posted by Fnord666 on Thursday October 24 2019, @04:27PM   Printer-friendly
from the an-organization-of-very-special-registers dept.

http://www.righto.com/2019/10/how-special-register-groups-invaded.html

Half a century ago, the puzzling phrase "special register groups" started showing up in definitions of "CPU", and it is still there. In this blog post, I uncover how special register groups went from an obscure feature in the Honeywell 800 mainframe to appearing in the Washington Post.

While researching old computers, I found a strange definition of "Central Processing Unit" that keeps appearing in different sources. From a book reprinted in 2017:1

"Central Processor Unit (CPU)—Part of a computer system which contains the main storage, arithmetic unit and special register groups. It performs arithmetic operations, controls instruction processing and provides timing signals."

At first glance, this definition seems okay, but a few moments thought reveals some problems. Storage is not part of the CPU. But more puzzling, what are special register groups? A CPU has registers, but "special register groups" is not a normal phrase.

It turns out that this definition has been used extensively for over half a century, even though it doesn't make sense, copied and modified from one source to another. Special register groups were a feature in the Honeywell 800 mainframe computer, introduced in 1959. Although this computer is long-forgotten, its impact inexplicably remains in many glossaries. The Honeywell 800 allowed eight programs to run on a single processor, switching between programs after every instruction.3 To support this, each program had a "special register group" in hardware, its own separate group of 32 registers (program counter, general-purpose registers, index registers, etc.).


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  • (Score: 2) by takyon on Friday October 25 2019, @01:18AM (3 children)

    by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Friday October 25 2019, @01:18AM (#911460) Journal

    Side-channel attack

    There's a network involved somewhere. Possibly a non-traditional one, or a compromised meatbag walking back to the spy handler.

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  • (Score: 2) by c0lo on Friday October 25 2019, @03:02AM (2 children)

    by c0lo (156) Subscriber Badge on Friday October 25 2019, @03:02AM (#911480) Journal

    Side-channel attack

    There's a network involved somewhere. Possibly a non-traditional one, or a compromised meatbag walking back to the spy handler.

    Mmmm-yeeaaah.
    Everything IO is a network and all network is Internet. Furthermore, all the storage is disk**, and then we can use whatever words we want to always say something true.
    For some values of true, that is, but that's OK, 'cause we're gonna to democratically debate anyway on what values of "true" are fakes††

    And now time for the breaking commentaries‡‡, stay with us for Acidly Scorpion Jugged-Earwig Putrescent [youtube.com] advice: turn on the captions

    Ham sandwich, bucket and water plastic Duralex rubber McFisheries underwear. Plugged rabbit emulsion, zinc custard without sustenance in kipling-duff geriatric scenery, maximises press insulating government grunting sapphire-clubs incidentally. But tonight, sam pan Bombay Bermuda in diphtheria rustic McAlpine splendour, rabbit and foot-foot-phooey jugs rapidly big biro ruveliners musk-green gauges micturate with nipples and tiptoe rusting machinery, rustically inclined. Good evening and welcome.

    ----

    ** and all registers are storage anyway. And there is no such thing as "special registers" or, at least, they don't make a group, or the group is nothing special. And CPU is that thingie there but definitely not the disc.

    †† because we are living in a post-truth society, baby. Wooohooo, your bloody engineering is no more valuable than my opinions. And thanks God for the second amendment, worse come to worst, we can eventually settle whatever arguments (over CPU or over any-and-all the other things) by having a civil - not necessarily civilized - war.

    ‡‡ those old bums used to call them "news", LOL.

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    • (Score: 2) by hendrikboom on Friday October 25 2019, @08:06PM (1 child)

      by hendrikboom (1125) Subscriber Badge on Friday October 25 2019, @08:06PM (#911836) Homepage Journal

      and all registers are storage anyway.

      On the Bendix G15d, the registers resided on a rotating magnetic drum.

      -- hendrik

      • (Score: 0) by Anonymous Coward on Saturday October 26 2019, @12:43AM

        by Anonymous Coward on Saturday October 26 2019, @12:43AM (#911935)

        And because one has registers on magnetic drums, all registers are storage. Got your point.