retro-computingnintendo

Retro video games programming

I just watched the Super Mario Bros. -1 World glitch in youtube and I really began wondering about the code behind those games. Which language was used? What about the OS for the video games consoles? Are there any website with resources about this subject? (I am a 90s video gamer so I am particularly interested about the programming behind those games but feel free to make this a wiki and include links to resources about video games programming in general, if you want)

Solution

  • Having somewhat worked on an emulator for the NES (I have it decoding some opcodes, but none of the other hardware is emulated), I can maybe share a few answers.

    1. For most games assembler was used. Optimizing compilers, if available for the CPU were nowhere near as good 20-30 years ago as they are today. To get performance, you needed to write in assembler (This even held true on the PC. Parts of Doom are in ASM). All the more so, since the NES CPU ran at less than 2MHz. Also, memory was more expensive then than it is today. The original Mario was stored in about 40k of memory. 16k of that was the actual code, and the remainder was the graphics and sound resources.

    2. Until the 32 bit console era, any sort of operating system, or even built in utilities, on a console was uncommon (Sega CD was the one of the few in the 16 bit era with an actual BIOS, and there was a small program burned into the Game Boy's processor that was responsible for the Nintendo logo scrolling down on power on). See above about size constraints, as a main reason. When inserting the cartridge, the ROM chip in the car was connected directly to the address bus of the CPU. On power on, the CPU would read from a fixed address to get the actual address the program started at, and then jumped to that location and started execution.

    As for resources, the NES Dev Wiki has resources concerning the NES hardware, along with programmming references. Zophar's Domain also has technical documents and public domain ROMs for quite a few console (I don't know if I should link to ZD on this site, just google it)