cctech Digest, Vol 52, Issue 29

[Bob Adamson]

The first LSI tester I ever worked on (manufactured by, I think, LSI
Testing Inc of Utah) used triple-66 bit MOS shift registers to store the
digital stimuli and compare patterns (3x64-bit registers plus 2 bits
used as control). Around 1970 or so at Hughes Microelectronics. Since we
manufactured MOS ICs (PMOS at the time) and the shift registers became
obsolete after a few years we designed our own as spares. The tester
itself used a PDP-8/L as the controller and was soon after replaced by a
bigger one which used a PDP8/I - my first contact with SEC PDP8
computers.

regards
Bob Adamson

 
> From: "Rick Bensene" <rickb at bensene.com>
> 
> A lot of early MOS shift registers were developed specifically for use
> in electronic calculators, as solid-state replacements for magnetic
core
> memory or magnetostrictive delay lines.  Since most all electronic
> calculators in the mid-'60's through the late 70's operated in BCD or
> some alternate four (or sometimes five)-bit representation of decimal
> digits, the shift registers were usually made with a number of stages
> that was a multiple of four or five, with a few extra bits here and
> there for timing and synchronization.  That's why many of these
devices
> as an unusual number of stages.  In some calculators from the late
> '60's, as IC logic had pretty much replaced discrete transistor
designs,
> there were different versions of the same machine, earlier machines
> which used a magnetostrictive delay line, and "updated" versions which
> dispensed with the delay line, and replaced it with a number of MOS IC
> shift register devices.  Functionally, the machines were identical. As
> far as the digital logic section of the machine went, also identical.
> The only real changes were the removal of the read amplifier and write
> driver for the delay line, and replacement with some simple
> level-shifting and power supply circuitry to properly drive the shift
> register chain.
> 
> Rick Bensene
> The Old Calculator Museum
> http://oldcalculatormuseum.com
>