#### Back to index | # Info for genesis

#### Sega Megadrive/Genesis (1988)

The Sega Genesis was released in Japan on the 29th of October 1988, and in the USA on the 1st of September 1989. At that time, no other console could compete with Sega´s powerful 16-bit system, apart from the PC-Engine / TurboGrafx-16, perhaps. But due to a lack of third-party support - especially with the arrival of the SNES, because many of the major game companies were still bound to Nintendo because of the contracts they made in the NES era - the Genesis never became as successful as Nintendo´s 16-bit console. Nevertheless, about 28.5 million consoles were sold worldwide, compared to about 48 million SNES consoles. Looking at the different regions of the world, the Genesis was most successful in the USA. It was quite strong in Europe, too (especially Great Britain is famous for being the European Sega stronghold), but did not succeed very well in Japan, Nintendo's home country. It was definitely no mistake to buy the console, as I did in early 1990, shortly after Super Shinobi had been released. Among t
he approximetaly 1000 games which were produced during the genesis' lifespan (about 10 years during 1988-1998) are a lot of evergreens which deserve to be played even today. (note taken from www.eidolons-inn.de)

Features:
Main Processor: Motorola M68000 (16-bit) at 7.67 Mhz
Co-processor: Z80a at 3.58Mhz
Sound Chips: YM2612 and a 4 channel TI PSG76489
Ram: 64k (Plus 64k Ram for sound)
Max Cart Size: ??

Video:
Max resolution: 320 X 224
Color palette: 512; 64 max on screen
Max # of sprites: 80; 20 max per scanline
Sound: Stereo FM-based sound with 8-bit audio samples

Usage:
Under the "Options" menu, accessible by hitting TAB, you will find the following option:
"Country" - this allows you to alter the 'flavour' of Genesis, to either European, Japanese or American. Many cartridges compare their country codes with that of the Genesis itself and may behave differently, or lock up if the two types do not match.
'Auto' attempts to auto-set the Genesis country code to the value the cartridge will appear to be checking for. This may not be 100% accurate, however.

Links:
EIdolons inn - www.eidolons-inn.de

MESS Emulation State:
Most games tend to run fairly well. Some have slight graphic glitches; incorrect colours part way down the screen or other bizarre effects. See genesis.crc for a partial list.
Cartridges up to 32MBit (4MByte) are supported.
The controller may not work well with some games. This will be resolved when more information is obtained. Similarly, 6-button joypads aren't emulated yet.
Split screen effects and interlacing are not yet supported.
Sprite/layer priority should be perfect.
Sound is emulated at Z80 and PSG76489 level.
I still consider the Genesis driver extremely preliminary. I have a lot of further work to do before I consider it anywhere near complete. My initial goal is to make it as compatible as possible. Currently there is scope within the driver to handle split screen colour changes/any VDP effect, interlacing, without rewriting. The graphics renderer emulates VDP at scanline level, and does not use tile-based methods.
Wanted: Any Sega Megadrive information specifically, some of the finer points of DMA transfer, and access of the 68K memory map by the Z80! Information is extremely sparse; typically the same three-four documents, with parts incomplete, conflicting, and corrupted. Generally, points which conflict with themselves in the documentation available on the net...

created on Mon Dec 09 08:16:57 2002