PDP11/55 sells on Ebay for 5K$ - was it really the fastest 11?

Lyle Bickley lbickley at bickleywest.com
Sun Apr 17 23:38:45 CDT 2005

On Sunday 17 April 2005 20:24, Heinz Wolter wrote:
> Don't want to start the old "Ebay ~is~ the market" thread up again... but
> on a technical note - the listing claimed that it was the fastest PDP11 of
> the blinkenlights
> machines made by DEC.. Is that true?
>  I expected  an 11/70 to be instruction for instruction faster - but
> add all the cache and complexity - maybe the 55 with bipolar ~was~ faster?
> How about compared to a 11/70 with a PEP70 instead of factory memory and
> cache?
> Isn't a 55 just a 45 with bipolar instead of core? or was that a 50?

Read "Computer Engineering" (Gorden Bell, J. Craig Mudge, John E. McNamara), 
Copyright 1978 by Digital Equipment Corporation

Page 408

Model   Basic Instructions Floating Point
        Inst. per second*   Inst. per second
11/70   36                 671
11/55   41                 725

* Relative to 11/03

No brainer - the 11/55 wins hands down.

Lyle Bickley
Bickley Consulting West Inc.
"Black holes are where God is dividing by zero"

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