You can also google for the various version of the system. System 1 is the one described in the book. System 4 consist of a very simple VM in C that implements only the byte code interpreter, memory management and garbage collection. Everything else is implemented in Smalltalk itself, including the compiler. The system is considerably smaller and easier to understand than a full Smalltalk 80 system.
System 4 appears to be archived at https://web.archive.org/web/20071005062021/http://www.little...
You can make use of a reference counting with cycle collector as basic GC implementation, without any JIT, for example.
When you say "the Blue Book", do you mean Inside Smalltalk: Volume I?
The Xerox PARC books about Smalltalk-80 are known by their cover colors, green, red and blue.
What we to do. Play the game ?