Re: The Seymour Cray Era of Supercomputers

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.