oldmachines · the collection
Interactive teardown · Sega · 1988

Inside the Sega Genesis

Explorable, hands-on explanations of how Sega's 16-bit machine — the Mega Drive outside North America — actually worked, one subsystem at a time. Not a spec sheet: each guide is a playable course you can hear, drag and toggle. Two CPUs, a tile-and-sprite video chip, and the FM synthesiser that gave the console its snarling voice — then, once the machine is taken apart, one course hands you the keys to write your own.

CPU Motorola 68000 · 7.67 MHz Sound CPU Zilog Z80 · 3.58 MHz Video Sega VDP · 320×224 Audio YM2612 FM + SN76489 Media ROM cartridge

Subsystems

CPU & the 68000

How processors work from zero, then the Genesis' two brains: the Motorola 68000 and its Z80 sidekick, the bus that makes them share memory, and how emulators run both in lockstep.

Ready · 15 modules

Graphics & the VDP

2D tile-and-sprite rendering from zero, then the Sega VDP: two scrolling planes, the sprite engine, line-by-line raster tricks, shadow/highlight, and how emulators redraw it a scanline at a time.

Ready · 16 modules

Audio · FM & PSG

Sound synthesis from zero, then the chips that defined the Genesis growl: the Yamaha YM2612 six-channel FM synth and the SN76489 PSG — operators, algorithms, envelopes — all played live in your browser.

Ready · 16 modules

The cartridge

ROM media from zero, then Genesis carts: the memory map, bank-switching mappers, the TMSS trademark check, Sonic & Knuckles lock-on, and the Sega CD / 32X on the edge connector — plus how emulators load a ROM.

Ready · 13 modules

Write your own homebrew

Build your own Genesis software with the free SGDK toolchain and m68k-elf-gcc — full setup on Windows, macOS and Linux, from an empty folder to your own code running in an emulator and on a real flashcart.

Ready · 13 modules