> I wrote a couple of programs for a Control Data Corporation (CDC) 6600 back
> in the early '70s. I recall that the smallest addressable unit was a 60 bit
> word (though there were special instructions to pack and unpack some size
> of character -- was it 6 bit?)
> Bob
Correct, except that there was also a 6/12 bit "display code" which
used a couple "escape" characters in combination with others to
expand the character set. There were several variants of both the
6-bit and 6/12 character sets. There weren't any hardware
instructions to do the packing and unpacking, but Greg Mansfield
had a couple very fast/clever routines that made use of a
floating point instruction to create a mask to let you switch
back & forth between words with blank fill and zero-bit fill.
Still, the smallest unit addressible by the CPU was the 60-bit
word. The PPUs (DMA I/O units) used 4096 12-bit bytes, IIRC.
The 7600 series broke the CPU up into functional units, such
that you could have a floating point operation, integer operation,
and Boolean operation executing simultaneously. These were still
illegal for export well into the 1980s. (Operating systems for
all the above included MACE [called by some Mansfield & Cahlander
Executive], EPIC [? a custom OS done for United Telecomm time-
sharing services], ZODIAC, Kronos, Scope & NOS.)
The later, 800 series, could run NOS and treat words as 60 bits
via micro-code, or NOS/VE native with 64 bit words and octet
addressibility. The spread of cheap UNIX boxes (among other
things) brought an end to their computer manufacturing operations.
The diverse conglomerate was repeatedly split during the 1980s &
1990s, with notable remnants including Ceridian, parent company
of Arbitron (the radio rating service). Some other units were
absorbed by Parametric Technologies (CAD/CAM/CAE), Primerica
(financial services), and Seagate.
John G. Otto Nisus Software, Engineering
www.infoclick.com www.mathhelp.com www.nisus.com software4usa.com
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My opinions are probably not those of Nisus Software, Inc.
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