AMSYS29 floppies - test-drb@ccmp.vtda.org

23 Nov 2010

Dave writes:

...
  On 11/22/10 4:12 PM, Tony Duell wrote: 
...
 >>   I have a S100 board that is said to be a
math processor board 
...
 >> that has a single 2901 on it. I have the
manual as well. 
...
 > 
...
 > I find that strange. A single 4 bit slice is not
that useful. I asusme 
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 > there arten;t 2903s as well :-) 
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     Well, 2901s were fairly expensive chips in those
days, and it's 
...
  certainly possible to do wider-than-four-bit math in a
four-bit CPU. :) 
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 > Althoguh AFAIK DEC never used them in a PDP11 CPU.
There were, of 
...
 > course, used i nteh floating point processors for
some PDP11s, and in the 
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 > VAX11/730 
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    And the KS10 as well.  I wonder if there are any
others; I don't 
...
  think so offhand. 
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   One of my favorite uses of Am2901s is in the FPF11
floating-point 
...
  processor.  For the non-PDP11-savvy, the FPF11 is a
strange board that 
...
  can be used in both Qbus and Unibus systems by
changing jumpers near the 
...
  card-edge connectors.  It uses a 40-pin ribbon cable
to plug into a 
...
  microm DIP socket in an F11-based PDP-11 (11/23 or
11/24). 
Off the top of my head... DEC also has 2901's in the CI780, and the UDA50, and
probably
A bunch of other peripherals/interconnects/host adapters I cannot recall at the moment.

Tim.