[TUHS] Why did PDPs become so popular?

Larry McVoy lm at mcvoy.com
Sat Dec 30 10:04:25 AEST 2017


On Fri, Dec 29, 2017 at 04:54:25PM -0700, Kevin Bowling wrote:
> I trust your judgement and experience WRT the Alpha.
> 
> If you're looking for massive performance deltas, what about ECL
> designs like the IBM 3090 and Cray designs in the late '80s/ early
> '90s?  I believe those were not a multiple but a magnitude faster than
> contemporaries.

For vector operations, yes.  For stuff that you and I care about,
running the OS, serving up data, not so much.

As I recall, the supercomputers were pretty crappy on anything that
wasn't a vector operation.  I helped port Unix to a CDC spinoff, the
ETA-10, and it was faster to cross compile stuff on a Sun 3/280 than
compile it natively.

I haven't run on either the 3090 or the Crays but I've got friends who
did (some of whom still work at Cray) and when I was crowing about what
I could do a Sun nobody told me that it was faster on a cray.

If you were doing scalar floating point, especially at the larger
precisions, yeah, the super computers were better.  If you were doing
that sort of thing as a vector, so a vector of 128 bit floats, yeah,
I could imagine that could be a lot faster than a Sun.  

SGI did a tick/tock where it was floating point focus, then integer focus.
It's possible that one of their floating point designs kept pace with the
super computers, I know that they went to the super computing conference
each year (I did the power wall over NFS at one).  But I don't know much
about floating point, never use it in my code :)

--lm


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