Genesis S-Video and Overclock

[chipperkwah]

Niode: If you look in the second picture at the top of the second page youll see a white cut in the middle of the picture, i think that is the cut that mmmonkey is referring to. The md2 guide definitely seems more difficult, Lifting the legs is a little scary but as long as you have a steady hand its not too difficult. If you have experience soldering you should be good.

Crux: The overclock doesn't require any resistors, everything on that board besides the oscillator is for the s-video amplifier. You follow the guide in exactly the same way, just swap the 9mhz oscillator with a 10 if you want to go faster. I went with the 10mhz clock speed, no glitches graphically or with the audio whatsoever, it runs flawlessly. The switch is exactly as basic as it sounds, wire the clock leg of the oscillator to one outside leg of the switch, the 7 mhz original clock speed from leg 14 of the cart slot to the other outside leg of the switch, and a wire from the middle leg of the switch to the clock leg of the chip. As long as you have a switch installed you can use the sega cd and the 32x with no issues.

[skate323k137]

Just finished all the mods on my model 1 genny, s-video, RCA, and overclock/stop switch.

The s-video guide here:
http://www-unix.ecs.umass.edu/~dhowland/mod/#svideo

which I believe is the one OP followed, is way more complex than necessary for the s-video circuit. I used that guide to find +5 and ground, but this one for the circuitry:

http://www.jamma-nation-x.com/jammax/neogeosvideo.html

Since the Neo has the same sony chip, I figured I'd give that a shot as it's much easier. All it takes is a cap/resistor on croma, and the transistor/resistor on luma. Output is amazing. No need to use a transistor/amp on croma. I used that method on both my genesis and my friends neo-geo.

As far as the overclock, I naively used the ~13mhz clock from the cart slot. I of course wired in a switch for the normal clock/over clock, and a momentary pushbutton next to it for the halt pin. Boot normal, hold halt, and flip the switch. However, many games do exhibit glitching, namely sonic 2 and 3. Funny enough, the original Sonic runs great on the 13mhz clock speed. Still, I'm going to get a 12mhz oscillator at some point for added stability and just switch b/t that and the normal clock. From what I've read, using an oscillator is usually more stable than the on-board 13mhz clock, even if the oscillator provides a faster clock speed.

[skate323k137]

Just did my friends model 1, I think it was a va-5. It had a cxa1145m instead of the standard cxa1145, which threw me off. The encoder is in the same place and I referenced it's data sheet to find the pin numbers were also the same (15 and 16). The chip and pins are far tinier than the cxa1145 i was used to, and the chip appears to be surface mounted so soldering to the bottom of the board wasn't going to happen. Either way, after a couple shoddy connection attempts on the Y pin, I was able to fix that and get it working flawlessly.

[Wobble The Hutt]

very nice! looks super clean! its on my list of things to do to my genesis (well the overclock, i use a RGB to VGA box i built/rebuilding to be more awesome)

[summittech]

Just finished the s video mod. Looks awesome!

[Amplibax]

Sorry to bump an old thread, but does anyone have a link to a guide for the s-video mod? All of the links in the thread seem to be down.

[Bikeage]

Here you go: http://www.risingstuff.com/forums/viewt ... f=16&t=744

[Amplibax]

Perfect, thanks, but holy blurry pictures batman. Those pictures are so out of focus I feel sick looking at them.

[Hatta]

Damn, I hate it when good pages like that go down. Archive.org isn't giving me anything either. I swear, I need to go through my bookmarks with wget and archive the lot of them.

[skate323k137]

http://www.jamma-nation-x.com/jammax/neogeosvideo.html

works, still present, and much simpler than the one OP followed. see my post above. I could crack open my model 1 genny if anyone needs pics of where to get +5 or ground, the rest is pretty simple.