Sega Genesis System Specs

Main CPU

• The main Central Processing Unit (CPU) of the Sega Genesis was the 32-bit Motorola 68000 (running in 16-bit mode), which was clocked at 7.67MHz. The 68000 was capable of addressing 16 MB from ROM (Read Only Memory), but was limited to 4 MB for game cartridges. It also had 64 KB of addressable (usable) RAM (Random Access Memory).

Co-processor

• The Sega Genesis used the Zilog Z80 as its co-processor and sound controller, and also provided some of the backward compatibility with the 8-bit Sega Master System (the Z80 was the Master System's main CPU). The Z80 was clocked at 3.58MHz, and had 8 KB each of work and sound RAM available to it, though it could also access 32 of the 68000's 64 KB of RAM for sound banking.

Sound CPUs

• The main sound CPU was the Yamaha YM2612, while the secondary was the Texas Instruments SN76489 PSG (Programmable Sound Generator) which was built into the Video Display Processor (VDP). Both sound CPUs were controlled by the Zilog Z80 co-processor. The YM2612 had 6 FM channels with four operators each, a low frequency oscillator and stereo panning. It ran at the same speed as the Motorola 68000. The SN76489 had a four-channel PSG, programmable noise and tone attenuation, three channels for square waves, and one channel for white noise generation. The SN76489 also worked with the Z80 to provide backward compatibility with the Master System.

Video CPU

• The VDP in the Genesis was the Texas Instruments TMS9918. It had a total palette of 512 colors, with three bits per color channel, but could only display up to 64 colors on screen at any given time. It could display up to three backgrounds at once and up to 80 sprites. Maximum screen resolution was 320 by 480 for PAL (Phase Alternate Line) and 256 by 480 for NTSC (National Television System Committee). Maximum resolution in Master System mode was 256 by 192. The Genesis VDP was capable of the Master System VDP's Mode 4 to complete the system backward compatibility. The VDP had 64 KB of video RAM, 64 KB of color RAM, and 40 KB of vertical scroll RAM.