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From: Michael S <already5chosen@yahoo.com>
Newsgroups: comp.arch
Subject: Re: The Seymour Cray Era of Supercomputers
Date: Wed, 21 May 2025 11:21:25 +0300
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On Tue, 20 May 2025 19:59:48 -0000 (UTC)
John Levine <johnl@taugh.com> wrote:

> According to Michael S  <already5chosen@yahoo.com>:
> >At time of introduction CDC 6600 was undoubtedly much faster both
> >than older [more expensive] IBM 7030 and than contemporary
> >[significantly less expensive] S/360 Model 50. But it was not
> >"orders of magnitude faster". Not even one order of magnitude
> >faster, except, may be, vs Model 50 in artificial very memory-light
> >floating-point intensive scenarios. 
> >High end S/360 (Model 65) came about half a year later. I would
> >imagine that for non-floating-point code it had about the same speed
> >as 6600.  
> 
> Those 360 models seem wrong.  The 360/50 was a midrange machine that
> shipped in August 1965, the /65 was a large machine that shipped
> in November 1964, 

Do you mean, November 1965?

> and the 360/75 was a high end machine that
> shipped in January 1966.  They were all announced at the same
> time, give or take IBM's replacing the paper 60 and 70 with the 
> faster 65 and 75.
> 

Sorry, I did not read Wikipedia articles about /50 and /65 with
sufficient attention and confused announcement with shipment. Didn't
realize that for /50 the time between announcement and shipment was
much longer than for /65.
W.r.t. CDC 6600 Wikipedia article does not state an exact date of the
1st shipment at all, just saying that it was in 1965.


> STRETCH was about 1.2 MIPS, the /50 was 0.133 scientific, 0.169
> commercial, the /65 was .563 and .567, and the /75 was .940 and .670,
> so only the /75 was a plausible replacement.  The high end machine
> was the /91 which shipped late and over budget in Oct 1967 and was
> much faster, 1.9 MIPS scientific and 1.8 MIPS commercial.  (I think
> the 91's actual commercial performance was much lower since it
> simulated decimal arithmetic in software, but nobody ran RPG programs
> on a /91.)
> 
> For concrete numbers a double precision floating point memory
> to register add on the /50 took 9.7us, /65 took 2.5us, /75 took .92us
> 
> Floating multiply was 47us, 7.7us, 4.1us.
> 
> The numbers for the /91 depended on whether the operands were
> available but if they were adds were 120ns, multiply 180ns.
> 
> The 6600 was reported to be three times faster than STRETCH which
> would have been 3.6 MIPS, a lot faster than any 360 of the time
> and well over an order of magnitude faster than the not particularly
> fast 360/50.
> 
> 
>