Sibbi's z80 reference page
very thorough, looks useful
Z80 Assembly
recommended on the fedi: guide to Z80 assembly
Jones on Arithmetic
tutorials on how to do "arithmetic on machines with just binary add, subtract, logical and shift operators, making no use of special hardware support for such complex operations as BCD arithmetic or multiplication and division" very good, very helpful
Z80 Assembly: Multiplication and division
nicely explained
What made the NES so interesting?
"Since I used my RetroUSB AVS for the NES footage to get its higher-quality HDMI output, and the Panasonic FS-A1F (an MSX2 machine) for the MSX footage so as to get its higher-quality RGB output, I've technically just compared the PPU (Picture Processing Unit, the NES' graphics chip) and the TMS9918A without actually using a real PPU or a real TMS9918A. Good job, Nicole." lmao
MUPS/16 - MMU
implementation of an MMU "from scratch" (i.e. a bunch of 74xx chips and some SRAM)
foobles' land
very small and good 8-bit RNG
Gameboy Development Forum / New to Game Boy programming, made a version of Snake
good tips toward stack allocation in gameboy assembly
Pico as Z80 RAM & RAM: Homebrew Retro Computer Part 2 – Maker Hacks
with just a little bit of micropython code. neat!
Russian multiplication - Atari 5200 / 8-bit Programming - AtariAge Forums
expansive thread on how to do multiplication with processors that don't have multiplication instructions