PDP11/55 sells on Ebay for 5K$ - was it really the fastest 11?
lbickley at bickleywest.com
Mon Apr 18 09:41:43 CDT 2005
On Monday 18 April 2005 07:05, Allison wrote:
> >> Read "Computer Engineering" (Gorden Bell, J. Craig Mudge, John E.
> >> 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.
> Sorry, while for those metric the 55 was a tad faster, for IO the 11/70 was
> massively faster. At that time to do large arrays of data you needed lots
> of fast IO to disks as you could only works with part of an array at any
> time due too addressing limitations of the PDP11.
> When you measure systems, measure the system not just the cpu.
System performance is application dependent.
If you were going to do FORTRAN FP, the 11/55 would be a good choice. This
specific 11/55 it was used as part of a flight simulator - a perfect
application for the high performance (CPU) 11/55.
If you were running a RSTS/E shop with lots of I/O (as I did many years ago),
your choice would have been an 11/70 - for it's massbus I/O capabilities,
good integer/FP performance, and memory capacity.
So saying it is the "fastest blinkenlights" system is certainly valid in the
context of its application - and in the manner that "Computer Engineering"
documented its performance.
Bickley Consulting West Inc.
"Black holes are where God is dividing by zero"
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