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  • Re: OoO execution

    From Lawrence D'Oliveiro@ldo@nz.invalid to comp.arch on Sat Jul 26 02:45:56 2025
    From Newsgroup: comp.arch

    On Wed, 16 Jul 2025 18:27:38 +0000, MitchAlsup1 wrote:

    The Anderson papers indicate the /91 was just heavily pipelined in the integer side.

    Not good enough to keep up with CDC?

    After about two years of promising that they would blow CDC out of the
    water ...
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  • From John Savard@quadibloc@invalid.invalid to comp.arch on Thu Jul 31 20:38:38 2025
    From Newsgroup: comp.arch

    On Sat, 26 Jul 2025 02:45:56 +0000, Lawrence D'Oliveiro wrote:

    Not good enough to keep up with CDC?

    After about two years of promising that they would blow CDC out of the
    water ...

    The IBM System/360 Model 91 wasn't even good enough to keep up with the
    Model 85.

    However, IBM still realized that OoO was useful, even if it delivered less
    than the promised improvement in performance. So they went on to the
    Model 195 which added cache to the Model 91 design. That did work well
    enough that *I think* it actually did out-perform the CDC machines of the
    time.

    Even if it didn't, it performed well, and could have been considered a
    superior alternative - the CDC 6600 had reliabillity problems, I remember reading. So it would only have had to come close to the 7600 or whatever
    CDC had at the time in such a situation.

    John Savard
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  • From Michael S@already5chosen@yahoo.com to comp.arch on Fri Aug 1 15:02:19 2025
    From Newsgroup: comp.arch

    On Thu, 31 Jul 2025 20:38:38 -0000 (UTC)
    John Savard <quadibloc@invalid.invalid> wrote:
    On Sat, 26 Jul 2025 02:45:56 +0000, Lawrence D'Oliveiro wrote:

    Not good enough to keep up with CDC?

    After about two years of promising that they would blow CDC out of
    the water ...

    The IBM System/360 Model 91 wasn't even good enough to keep up with
    the Model 85.

    However, IBM still realized that OoO was useful, even if it delivered
    less than the promised improvement in performance. So they went on to
    the Model 195 which added cache to the Model 91 design. That did work
    well enough that *I think* it actually did out-perform the CDC
    machines of the time.

    From what I see in Wkipedia, it looks like all "number-crunching
    oriented" S/360 Models, i.e. 85, 91 and 195, were failures from
    business POV, even if to slightly different degrees (85 less bad).
    May be, S/370 Model 195 was more successful, I was not able to find info
    about number of units shipped.
    But, then again, CDC 7600, despite its excellent performance, was
    significantly less successful commercially than 6600. So, may be, it was
    just a bad era for that type of machines.
    Even if it didn't, it performed well, and could have been considered a superior alternative - the CDC 6600 had reliabillity problems, I
    remember reading. So it would only have had to come close to the 7600
    or whatever CDC had at the time in such a situation.

    John Savard
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  • From John Levine@johnl@taugh.com to comp.arch on Fri Aug 1 15:44:52 2025
    From Newsgroup: comp.arch

    According to Michael S <already5chosen@yahoo.com>:
    From what I see in Wkipedia, it looks like all "number-crunching
    oriented" S/360 Models, i.e. 85, 91 and 195, were failures from
    business POV, even if to slightly different degrees (85 less bad).
    May be, S/370 Model 195 was more successful, I was not able to find info >about number of units shipped.

    Neither can I but I don't think it was very many.

    The /91 was a very unbalanced machine. For general computing
    like compilers it was about the same speed as the /85, but
    for floating point codes it was twice as fast or more depending
    on how well the code was tuned to the /91.

    The IBM history book says the /85 was a technical success largely
    due to the cache but didn't sell well, partly due to poor economic
    conditions, partly because customers wanted something faster and
    cheaper built using integrated circuits.
    --
    Regards,
    John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies",
    Please consider the environment before reading this e-mail. https://jl.ly
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