As far as I could tell looking around the project a bit, they configure the boot sector of a USB/CD/DVD/ISO to jump directly into a pre-built lisp image, no ass

As far as I could tell looking around the project a bit, they configure the boot sector of a USB/CD/DVD/ISO to jump directly into a pre-built lisp image, no assembly/C code required. At the very least least, the paging system, IO, GC definitely seem to be written in pure Lisp. They do compile the initial Mezzano image using SBCL, which is partly written in C, but it seems that they don't depend on any SBCL/C code on the machine that they control. I'm definitely not an expert though, I may be completely wrong about this :)