This is my series of articles about creating a C64 emulator inside GameMaker Studio.
At some point I’ll update it to be GameMaker Studio 2, but it’s pretty much the same, so should still be fine for folk to follow along with.

Introduction and Basic Emulation
6502 CPU flags and instruction emulation
Fixing emulation and C64 Memory Mapping
Drawing the screen
Creating Dynamic Sprites
Dynamic characters and raster splits
Adding SID Music