VDP

The VDP, also known as Video Display Processor, handles all video output on the Mega Drive. The VDP is often known as the YM7101, which is derived from the Sega Master System VDP for backwards compatibility. The Master System VDP is in turn derived from the Texas Instruments TMS9918A. In most (if not all) Mega Drive models, the VDP is a dedicated large chip on the main motherboard.

It has 64 KB of VRAM, which can be used to store patterns (also known as art) plane and sprite name tables, as well as horizontal scroll data. The benefit of storing name tables and H-Scroll in VRAM is that you can decide where this data is stored, but leaves less room for art. The VDP has 64 bytes of 9-bit RAM to store palettes. This special area of the VDP is known as CRAM, or Colour RAM.