PS, standing for "Portable Smalltalk" or more aptly "Peter's Smalltalk", was PARC's first and only implementation of Smalltalk-80 on a conventional (rather than microprogrammed) processor.

It was developed by PeterDeutsch and AllanSchiffman circa 1982
although Peter did almost all of the work in the end. They published a paper about it in the 1984 ACM Principles of Programming Languages conference called "Efficient Implementation of the Smalltalk-80 System".  http://www.daimi.au.dk/~ups/OOVM/papers/deutsch-schiffman-popl84.pdf

PS pioneered JustInTimeCompilation (which the paper calls "DynamicTranslation"), InlineCaching for message sends (i.e., polymorphic function calls) and multiple context (i.e., reified activations) representations. Subsequent implementations of the SmalltalkLanguage and Smalltalk-like languages would use all of these techniques.

PS was written entirely in AssemblyLanguage for the Motorola 68000. It was originally targeted to a bare metal (no OS) SUN-1 workstation hand built by Allan from Andy Bechtolsheim's second set of PC boards. Later it would be rehosted on the SUN-2 running SunOS and shipped as ParcPlace's first product, Objectworks version 2.3. It wasn't portable, of course, but the successor implementation -- HighlyPortableSmalltalk -- was.

Other people who worked on PS were Mike Braca, Bob Hagmann and Mike Roberts. The port to the Sun-2 was done by Ron Carter and Russ Pencin, then of Xerox in Texas, later of ParcPlace.

Contributed by AllanSchiffman on 3-Aug-02.