15 Nov
2017
15 Nov
'17
1:57 p.m.
On 11/15/2017 11:59 AM, Rick Bensene via cctalk wrote:
While the definition of the term "personal
computer" varies depending
on who is using the term, these machines, and others like them, were
designed to be used at a much more personal level than the large-scale
mainframe machines housed in the glass-walled rooms where only "special"
people were allowed anywhere near them.
Chuck responded:
How about "small systems", able to be powered
solely from a 115V/20A source (or its 220V equivalent)?
The PB 250 would certainly fall in this category also.
Indeed, a notable omission from my list.
The PB 250 definitely is in that class of machine, and the unique part about it is that
its main memory and register storage was made of recirculating delay lines. This made the
machine somewhat slow, but in most cases, a bit faster than most of the tube-based
machines with magnetic drum memories. The delay lines could be a little temperamental,
but were less expensive than magnetic drums, making the machine a pretty good value for
the time. It was fully-transistorized, and had a Friden Flexowriter for I/O. The machine
had interfacing capabilities that allowed a number of various I/O devices to be connected
to it.
The PB 250 benefitted from the design genius of Stanley Frankel, the Manhattan Project
nuclear physicist that went into computing after his A-bomb development work had finished.
Frankel assisted with many of the design aspects of the PB 250, as well as doing the
complete logic design of the LGP-30, which was based on a small machine he built on his
own known as MINAC. He also did the design of the SCM/Marchant Cogito 240 & 240SR
electronic calculators, as well as the brilliantly-designed, microcoded Diehl Combitron
electronic calculator.
-Rick
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Rick Bensene
The Old Calculator Museum
http://oldcalculatormuseum.com