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

Sega Megadrive/Genesis (1988)
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Bios = None required
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 the 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
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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
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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
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EIdolons inn - www.eidolons-inn.de
MESS Emulation State
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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 Wed May 15 07:18:19 2002