The answer to a lot of "wow, how did the 8-bit machine pull that off? it seems like that would eat a lot of RAM" is that the framebuffer is the data storage. You were literally looking at the primary data store itself, because when a full-resolution framebuffer was 1/4th your addressable RAM (and slightly more than that for your actual RAM since you couldn't ever quite use all 64KB no matter how you mapped it), you need to get the most bang for the buck out of that RAM usage as you can.
Ha, I remember doing this with my Apple //. I forget what I was doing, but realized if I could set a pixel and later get what color was drawn at that location I could use it as a big array. Didn't know about peek/poke yet. One of those core "computers are magic" memories.
