The recent interesting discussion of performance and vm architectures
motivated to get permission to publish the specification of one of the
architectures I developed over the years. It can be found at:
http://www.smalltalksystems.com/publications/avmarch.pdf

The following is from the document's introduction:

This document  describes a bytecode architecture for an experimental
Smalltalk virtual machine.  The architecture was originally developed by
the authors at Digitalk Inc. in 1993-1994.  This document is published with
the permission of ObjectShare Inc, the successor company to Digitalk.

This architecture is intended to be used for the representation of compiled
method in the context of dynamic translating ("JIT") virtual machine. As
such, its main purpose is to provide information that can be easily and
efficiently processed by such a translator. An important design goal was
the minimization of the space needed to represent compiled methods.
Because it was design to be the input to a translator, minimization of
decoding time was not a consideration of the design. It was not intended
for direct interpretation and certain features, such as the "Label"
construct would be inefficient if used by an interpreter.

Allen_Wirfs-Brock at Instantiations.com