Genesis Facts

evildragon · Post by **evildragon** » Sat Sep 30, 2006 11:35 pm

I have compiled some facts about the Genesis, that I have found from experiments, and from rare and hard to find websites.. Thought this would help, when someone is modding the console, or choosing an LCD.

The Sega Genesis' highest resolution is not 320x240, but 640x480.

The cartridge port has TWO audio lines (pins B1 and B3, for stereo sound), and the Genesis is quite capable of mixing it. (from what I have seen, the only thing to actually use those pins is the Sega 32X -for it's 10-bit PCM channel-)

The 32X does not run on it's own, as far as Graphics are concerned.. For example, when playing Knuckles Chaotixs, the level design is drawn by the Genesis, while the characters, items, rings, and HUD are drawn by the 32X... (that's what the passthrough cable is for, it's so the 32X can OVERLAY graphics)

Genesis model 1 has cleaner audio than a model 2.. The DAC in the model 2 is (very slightly), more scratchy than the model 1. I have traced this down to being the CPU used in the model 2 (while it's the same chip, it's a smaller package, so something was cheeped out on it)

While hated, the YM2612 used in the Genesis ain't that bad of a synthesizer, it can run patches from a Yamaha DX100 synthesizer easily (which was used for some games)..

I will try and add more facts, when I remember them.. Feel free to comment on any of the facts.. They are all true facts, and I will explain them in more detail if you'd like...

atari2600a · Post by **atari2600a** » Sat Sep 30, 2006 11:58 pm

Where there any games that utilized 640X480?

evildragon · Post by **evildragon** » Sun Oct 01, 2006 12:10 am

atari2600a wrote:Where there any games that utilized 640X480?

The Sonic 2 split screen used the 640x480 mode (640x448 for USA and Japan) (you can even tell too, it's interlaced when in that mode)..

There was a racing game that used the high-res mode, but I can't remember the name..

Also, a demo-cart, that Censor one that has the C64 graphics on it, when played on the real Genesis, runs in full 640x448/480 mode (no splitscreen, I mean full-screen)...

Sadly, emulators don't take this into consideration, and chop Sonic 2 split screen into the low-res.. KEGA Fusion (when in doubled mode), DOES take this into consideration, and shows full resolution...

Give me a few minutes, and i'll get a screenshot of KEGA Fusion in sonic 2 split-screen, and you can easily see the higher resolution (sonic 2 actually uses a 320x448/480 mode, but the vertical resolution is still doubled)

evildragon · Post by **evildragon** » Sun Oct 01, 2006 12:15 am

here it is..

http://blackevilweredragon.spymac.com/sonic2.JPG

sonic two runs in 320x448 (320x480 for PAL) when in splitscreen.. reason for this, is so that way the play fields are still 320x224/240, as they are in single player mode..

though, like i said, one racing game, and the censor C64 graphic demo, use the full-screen 640x480 mode...

here's the Censor graphic demo..

notice the pixels aren't doubled, they are perfect high-res sprites...
http://blackevilweredragon.spymac.com/genhighres.PNG

atari2600a · Post by **atari2600a** » Sun Oct 01, 2006 1:10 am

Nice! (Remember to use PNG or BMP for screenshots; JPG compression looks like crap!

)

evildragon · Post by **evildragon** » Sun Oct 01, 2006 1:16 am

atari2600a wrote:Nice! (Remember to use PNG or BMP for screenshots; JPG compression looks like crap! )

Yea, that's why I used the PNG for the second screenshot.. I forgot completely that I had JPEG selected, till after the file was uploaded...

EDIT: I am sure, with this information, any mini-Genesis hack, should include an LCD that can actually handle this high-res mode, without needing to down-scale it... Because since the Genesis can do it, why limit it?

atari2600a · Post by **atari2600a** » Sun Oct 01, 2006 1:25 am

Hey, do you know if the CPU in the Genesis 3 has the scratchy sound the Genesis 2 has? (I have a Genny3 mobo I plan to portablize)

evildragon · Post by **evildragon** » Sun Oct 01, 2006 1:28 am

atari2600a wrote:Hey, do you know if the CPU in the Genesis 3 has the scratchy sound the Genesis 2 has? (I have a Genny3 mobo I plan to portablize)

I have no clue, never seen or used a model 3.. Knowing it isn't manufactured by SEGA, and uses even more single chip designs (i think atleast), I would say it probably does...

The scratchyness only affects the YM2612s DAC (like when it says "SEGA" on Sonic, it don't sound as clear as a model 1 does) The reason I think it's the CPU, even though the YM2612 plays it through it's DAC, is because it's NOT buffered, and though the Z80 does the music and sound, the MC68000 has to send the sounds to the YM2612 itself.. and it seems that the smaller form factor version of that chip, like used in the model 2, just don't seem good at it, as the model 1 is..

evildragon · Post by **evildragon** » Sun Oct 01, 2006 1:31 am

Here's another fact I just remembered, before going to sleep..

When the 32X is attached, the graphics ARE cleaner (atleast on a model 1 genesis)..

Reason: The 32X only cares about the RGB signal from the Genesis when it handles the overlaying of graphics.. Even though when a Genesis game is used, and the 32x is in a standby state, the 32X still takes that RGB signal, and converts it to NTSC composite via it's OWN encoder chip.. The encoder chip used in the 32x is better than the chip used in the Genesis model 1.. This results in a more cleaner picture (less colored bands in heavily dithered areas)

atari2600a · Post by **atari2600a** » Sun Oct 01, 2006 1:32 am

Here's the Genesis 3 mobo:
<img src="http://www.gamesx.com/grafx/gen3over.jpg">

evildragon · Post by **evildragon** » Sun Oct 01, 2006 1:49 am

Wow, totally a single-chip design, I don't even see the CPU at all..

It probably will have distorted sound, but it could also be better.. I wouldn't know, without hearing Sonic 2 starting, and saying "SEGA".. (as I can compare them)

Post by **Skyone** » Sun Oct 01, 2006 1:54 am

Ya, it uses a multi-processing chip.

evildragon · Post by **evildragon** » Sun Oct 01, 2006 2:29 pm

Btw, I know my web server hosting company is having down time (again), so the links don't work right now... If they don't get the server fixed by tonight, I will put the images on my Photobucket..