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The most interesting part to me is how often emulator development turns into discovering that the original games were doing something deeply strange but complet

The most interesting part to me is how often emulator development turns into discovering that the original games were doing something deeply strange but completely intentional

jonhohle 7mo ago
I’ve been decompiling for the past (almost) two years, and it’s fun to see the bugs, compiler quirks, programmer superstitions, things that coincidentally work because of compiler behavior not because of correctness, as well as the things modern tooling would have caught that 30-year old versions of GCC hadn’t gotten around to yet. There were even things I thought I had to manually optimize in the early 2000s that the GCC optimizer was already taking care of in the mid-90s.
- WalterGR 7mo ago
  Have you written about your discoveries anywhere? They sound pretty interesting.
- thesuitonym 7mo ago
  How can you tell the difference between something manually optimized and something automatically optimized?
  - Philpax 7mo ago
    There's not really an exact science to it, but manually-optimised code is usually more structured/systematic to make it easier for the human author to manage the dependencies and state across the board, while automatically-optimised code is free to arrange things however it would like. As an example of the kinds of optimisations that the best human programmers were doing before compilers took over, see Michael Abrash's Black Book: https://www.phatcode.net/res/224/files/html/index.html https://www.phatcode.net/res/224/files/html/index.html - you can intuit how a human might organise their code to make the most of these while still keeping it maintainable.
- deleted 7mo ago
  [deleted]
anthk 7mo ago
Heh. Today I found thanks to the 9front people that some GB games used carts' sram as 'swap'. games/gb didn't save the sram in the emulator save files, so upon restoring the snapshot and saving in the cartridge memory you got a mismatch. It got fixed really fast, the emulators are really simple plan9 C compared to anything else.

The most interesting part to me is how often emulator development turns into discovering that the original games were doing something deeply strange but completely intentional

jonhohle 7mo ago

I’ve been decompiling for the past (almost) two years, and it’s fun to see the bugs, compiler quirks, programmer superstitions, things that coincidentally work because of compiler behavior not because of correctness, as well as the things modern tooling would have caught that 30-year old versions of GCC hadn’t gotten around to yet. There were even things I thought I had to manually optimize in the early 2000s that the GCC optimizer was already taking care of in the mid-90s.

WalterGR 7mo ago
Have you written about your discoveries anywhere? They sound pretty interesting.
thesuitonym 7mo ago
How can you tell the difference between something manually optimized and something automatically optimized?
- Philpax 7mo ago
  There's not really an exact science to it, but manually-optimised code is usually more structured/systematic to make it easier for the human author to manage the dependencies and state across the board, while automatically-optimised code is free to arrange things however it would like. As an example of the kinds of optimisations that the best human programmers were doing before compilers took over, see Michael Abrash's Black Book: https://www.phatcode.net/res/224/files/html/index.html https://www.phatcode.net/res/224/files/html/index.html - you can intuit how a human might organise their code to make the most of these while still keeping it maintainable.
deleted 7mo ago
[deleted]

anthk 7mo ago

Heh. Today I found thanks to the 9front people that some GB games used carts' sram as 'swap'. games/gb didn't save the sram in the emulator save files, so upon restoring the snapshot and saving in the cartridge memory you got a mismatch. It got fixed really fast, the emulators are really simple plan9 C compared to anything else.