This chapter describes many aspects of OpenMCL's implementation as of (roughly) version 1.1. Details vary a bit between the three architectures (PPC32, PPC64, and x86-64) currently supported and those details change over time, so the definitive reference is the source code (especially some files in the ccl/compiler/ directory whose names contain the string "arch" and some files in the ccl/lisp-kernel/ directory whose names contain the string "constants".) Hopefully, this chapter will make it easier for someone who's interested to read and understand the contents of those files.