I’m a loooong-time Smalltalk VM implementor having done my first VM in 1983. I was lucky enough to work on Peter Deutsch’s HPS VM for VisualWorks throughout the 90’s and early 2000’s and essentially double its speed (mostly by adding polymorphic inline caches and rearchitecting its mapping of contexts to stacks). I was technical lead for VisualWorks from vw 3.0 through vw 7.4.1, leaving at the and of 2006. I spent an all too brief but stimulating time at Cadence in Gilad Bracha’s Newspeak team. I’m now at Teleplace (née Qwaq) where I’m free to implement another fast VM for Croquet, a 3d immersive collaboration architecture built above Squeak Smalltalk, but this time (unlike VisualWorks) the VM is open source. This blog is intended to communicate the design and evolution of the Cog VM to the community at large, amongst collaborators and spectators alike.