Article 33591 of comp.sys.amiga.programmer: Newsgroups: rec.games.video.sega,alt.sega.genesis,comp.sys.amiga.programmer Path: news.csos.orst.edu!flop.ENGR.ORST.EDU!gaia.ucs.orst.edu!umn.edu!news-feed-1.peachnet.edu!darwin.sura.net!howland.reston.ans.net!math.ohio-state.edu!cs.utexas.edu!swrinde!elroy.jpl.nasa.gov!decwrl!netcomsv!netcom.com!dash From: dash@netcom.com (David Ashley) Subject: Brief description of Genesis Hardware Message-ID: Organization: xxx Date: Thu, 17 Jun 1993 21:27:45 GMT Lines: 51 Xref: news.csos.orst.edu rec.games.video.sega:2272 alt.sega.genesis:1812 comp.sys.amiga.programmer:33591 Some people have posted questions about the Genesis internals--maybe this will be of some use... Sega Genesis Brief Technical Specification The Genesis uses a tile approach to all graphics. Tiles are 8x8 pixels, 4 bits/pixel, allowing for 16 colors. There are two playfields, which are made up of pointers to tiles in 32x64 arrays. Each tile pointer contains the tile number (2048 tiles possible in 64k graphics ram) and bits for flipX, flipY, and two bits which select which of the four color tables to use. On screen there are 224 lines by maybe 336 pixels, or 28 tiles vertical by 42 tiles horizontal. The two playfields can be scrolled independently in both directions. A single tile requires 32 bytes. There are four color tables, each of 16 entries. There are 3 bits/gun. There can be up to 80 sprites. Sprites are built up of tiles, and can be from 1 to 4 tiles wide and from 1 to 4 tiles high. There can be about 20 16 pixel wide sprites on a scan line, or about 10 32 pixel wide sprites. Sprites also have flipx and flipy bits, and color table select. Sprites can have transparent. Audio hardware consists of a Yamaha FM Synthesis chip, with 6 voices and four operators/voice. Each voice has its own parameters. There is a digital channel for playback of digital samples. Also there is a simple programmable sound generator that has 3 square waves and one white noise generator. The 68000 runs at slightly less than 8 mhz. It has 64K of RAM. The Z80 has 8k of ram, but can access all of the 68000's memory. There is 64k of graphics ram, allowing for 2048 tiles maximum (allowing no other memory for playfields and sprites and such). There is a simple DMA copier that can quickly do copies from the 68000's address space to the graphics memory. Vertical and Horizontal blank interrupts can be activated on the 68000. Joysticks are read by the 68000 through a simple routine. Bits for the joystick are memory mapped. In general the Genesis is VERY easy to program--the hardware is quite powerful. PLUG: Contact me about development systems. -- David Ashley dash@netcom.com