Question 1

How do I set up Gameboy Doctor with my Game Boy emulator?

Accepted Answer

You need to tweak your emulator to initialize CPU state post-boot ROM, hardcode the LY register to return 0x90, and log CPU state after each opcode in the specified format. Then, run Gameboy Doctor with the log file and ROM parameters as detailed in the README.

Question 2

Gameboy Doctor or manual logging for debugging emulators?

Accepted Answer

Gameboy Doctor automates comparison against a known-good reference, saving hours over manual tracing, but requires upfront emulator modifications. For quick, one-off checks, manual logging might be simpler, but for systematic bug isolation, Gameboy Doctor is more efficient.

Question 3

Does Gameboy Doctor support other test ROMs like dmg-acid2?

Accepted Answer

No, it currently only supports Blargg's cpu_instrs test ROMs. The README mentions future work to expand support, but for now, it's limited to CPU instruction debugging, so you'll need other tools for graphics or comprehensive tests.

Question 4

How to interpret the error output from Gameboy Doctor?

Accepted Answer

The output shows mismatched register values, the previous CPU state, and the last opcode executed. Focus on the diverged register (e.g., A in the example) and the opcode hint (e.g., LD (DE) A) to identify implementation errors in your emulator's CPU or interrupt handling.

Question 5

Can I use Gameboy Doctor on Windows?

Accepted Answer

Yes, the README notes that on Windows, you may need to invoke the Python interpreter directly with 'python3 gameboy-doctor', as the script might not execute directly due to system differences.

Question 6

How to pipe my emulator's output to Gameboy Doctor in real-time?

Accepted Answer

Set the logfile path to '-' and pipe your emulator's output: for example, 'your-emulator | gameboy-doctor - cpu_instrs 3'. This streams data directly, allowing for immediate divergence detection during execution.

Game Boy Doctor

What is Game Boy Doctor?

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