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Cogwheel is software emulator primarily for 8-bit Sega hardware, such as the Sega Master System, Sega Game Gear and SG-1000. The ColecoVision is also supported.

The project uses a modular design based around a Z80 core emulator class library. The rest of the Sega-specific emulation is implemented in another class library, and the user interface is implemented as a separate application. This would allow the main emulator to be easily adapted to different interfaces.

The code is written in C# 3.0 (targetting .NET 2.0). The user interface uses Windows Forms, with SlimDX being used to render the graphical output to the form as quickly as possible.

The following features are currently supported:

  • Z80 CPU (emulates all documented and most undocumented features).
  • TMS9918A video with custom Sega VDP Master System and Game Gear extensions. Supports multiple versions (hardware revisions, PAL/NTSC) and emulates bugs depending on version.
  • SN76489 (PSG) sound.
  • YM2413 (FM) sound.
  • Standard ROM mapper, Codemasters mapper and a 64KB RAM mapper.
  • Sega and ColecoVision joypad emulation.
  • Hardware profiles for SG-1000, SC-3000, SMS1, SMS2, Game Gear and ColecoVision.
  • Japanese/Export hardware differences.