The author of Chicken Scheme, Peter Bex, has the best explanation of #scheme internals that I have seen anywhere on the Internet.

I saw one of these linked around Fedi, but now I can't find where I saw it, so I guess I'll repost it along with the rest of what I found.

• https://www.more-magic.net/posts/internals-data-representation.html: This is the best place to start. It talks about the pointer tagging, how immediate values are distinguished from pointers to block objects. It calls out to:
• https://www.more-magic.net/posts/internals-gc.html. This is the Cheney algorithm. This gets into Chicken's really hairy continuation-passing stuff and rolls out C setjmp and longjmp to deal with it.

Both of these have LOTS of references to good old AIM papers and other meaty references scattered around the Internet, which as Bex points out, are quite difficult to find, so I am thankful to him for gathering them!