Gearsystem is really good at MSystem, GGear, SGone thousand, and O. Doublevision systems.

• Accurate core, including undocumented opcodes and behavior like R and MEMPTR registers.
  
• Automatic region detection.
  
• Accurate VDP emulation including timing and 2 only 224 video mode support.
  
• Internal database for content detection.
  
• Sound emulation using SDL Audio and very popular audio library.
  
• Battery powered RAM save support.