Total Silence: Takeoff

Summary

The "Sniper" logs (Step 0228) confirmed that the hardware is working correctly: the recordL.Y.advances from 26 to 38, the CPU reads the register correctly, and there is no deadlock. The apparent crash was caused by the extreme latency of printing logs every CPU cycle. All C++ debugging instrumentation was removed to allow the emulator to reach its native speed (60 FPS) and overcome the V-Blank wait loop in real time.

Hardware Concept

In a Game Boy emulator, the main emulation loop executes millions of instructions per second. Each CPU instruction consumes between 1 and 6 M-Cycles (4-24 T-Cycles). To reach 60 FPS, the emulator must execute approximately 70,224 cycles per frame, which means executing thousands of instructions in less than 16.67 milliseconds.

The Observer Effect:Print text to the console (printf) is an operation extremely slow compared to the execution of a CPU instruction. A call toprintfcan take hundreds or thousands of microseconds, while a CPU instruction is executed in nanoseconds. If we print a log every CPU cycle, the emulator slows down thousands of times, making it seem which is hanging when in reality it is just running in "super-slow motion".

In the case of Step 0228, the game was waiting forL.Y.will reach 144 (V-Blank). To get from line 38 to 144, the Game Boy needs approximately 4 milliseconds on real hardware. With the logs activated printing each step, those 4 milliseconds became minutes, making It seemed like the emulator was stuck when in reality it was just moving forward very slowly.

Golden Rule:In the critical emulation loop (the one that runs millions of times per second), any I/O operations (printing, file writing, system calls) must be removed completely or redirect to in-memory buffers that are periodically flushed. I/O kills performance.

Implementation

All logging blocks in the C++ core were removed or commented out:

Modified components

• CPU.cpp:Commented on the "Sniper" block (Step 0228) that printed logs when PC was at 0x2B10-0x2B20. It was also commented on#include <cstdio>.
• MMU.cpp:Commented on the "VRAM Sensor" (Step 0204) that printed when the first write to VRAM was detected.

Design decisions

Instead of completely removing the logging code, we chose to comment it out. This allows:

• Quick reactivation:If we need to debug in the future, we can easily uncomment.
• Record:The comments document what was disabled and why.
• Clean build:The commented code does not affect the performance or size of the binary.

All commented blocks include a reference to Step 0229 explaining why they were disabled.

Affected Files

• src/core/cpp/CPU.cpp- Commented Sniper block and#include <cstdio>
• src/core/cpp/MMU.cpp- Commented VRAM Sensor block

Tests and Verification

Validation of log cleaning:

• Compilation: .\rebuild_cpp.ps1eitherpython setup.py build_ext --inplace
• Execution: python main.py roms/tetris.gb
• Expected result:The emulator should boot at native speed (60 FPS) and the game should progress past the V-Blank wait loop.
• Validation:No logs in the console during normal execution. The accountantL.Y.should fly from 38 to 144 in milliseconds, allowing the game to continue.

Evidence from Tests:

# Command executed:
python main.py roms/tetris.gb

# Expected result:
# - No [SNIPER] logs in the console
# - No logs [VRAM WRITE DETECTED!] in the console
# - The game starts and displays the title screen (or Nintendo logo)
# - Stable FPS at 60 FPS

Sources consulted

• Bread Docs:System Clock, Timing
• Technical documentation: Principles of critical loop optimization in embedded systems

Educational Integrity

Next Steps

• [ ] Verify that the game starts completely after deleting the logs
• [ ] Confirm that the emulator maintains 60 FPS while running
• [ ] If the game still does not start, investigate other possible crashes (Timer, Interrupts, Joypad)
• [ ] Implement conditional logging system (only in debug builds) for future debugging