When you dump a physical Mega Man X2 cartridge, you get the main program ROM (the game code) and the graphics/sound data. However, the Cx4 chip is a separate piece of hardware. If you run the raw ROM on an emulator, the emulated SNES CPU will send commands to nothing —the Cx4 chip is missing.
| Chip Name | Used In | Purpose | Emulation File(s) | | :--- | :--- | :--- | :--- | | | Mega Man X2, X3 | Rotation, scaling, wireframes | cx4.bin | | Super FX | Star Fox, Yoshi’s Island | 3D polygon rendering | sfx.bin , sfx2.bin | | DSP-1 | Pilotwings, Mario Kart | Math calculations (Mode 7 matrix) | dsp1.bin , dsp1a.bin | | SA-1 | Super Mario RPG, Kirby Super Star | Faster CPU (10x SNES speed) | sa1.bin | cx4.bin
As of 2025, the conversation around cx4.bin has evolved. With the rise of FPGA-based consoles (like the and Analogue Pocket with the Dock), users are no longer using software emulation. Instead, they are recreating the hardware logic itself. When you dump a physical Mega Man X2
Modern emulators like and bsnes/higan have built-in checks. If cx4.bin is missing, they will display a specific error message: "Missing required DSP/Cx4 firmware." | Chip Name | Used In | Purpose
In the context of emulation, cx4.bin (often referred to as a "BIOS" or "special chip image") contains the internal data ROM dumped from the original physical chip. While early emulators struggled to run games like Mega Man X2 because they lacked the "brain" of the cartridge, modern "Low-Level Emulation" (LLE) uses this file to replicate the chip's functions exactly as they occurred on original hardware.