Genesis does... SLI

[Jorge Nuno]

In the genvdp.txt doc it says that the VDP could potentially have an overlay capability leftover from the TMS9918. So this thing crossed my mind in the past few days while messing with the VDP looking for unused bits/pins/crap etc. If that capability was indeed present, that would mean I could connect 2 megadrives together, or more generally, a megadrive and another system while sharing the same audio and video outputs. So yeah I did some work on it to see if it was possible and.. yes it is!

I had the idea of building a "MDX2", a system having 2 megadrive boards, 2 slots and 2 controller ports while sharing the same AV (they would be superimposed on each other). The idea is playing 2 single player games (same game or not) as it was multiplayer, maybe with a random timer to switch controllers electronically :V


A while ago I connected a Gen3 to an MD1, the MD1 acting as a slave device running a program made by me (that sets up the VDP for Sync input), but sadly it requires heavy mods on the system to pull it off (and maybe patching the games)


22062011113.jpg 22062011116.jpg

What you see here is 2 MD, 1 running S&K, the other running my program with their RGB lines connected together.

As I said before, the sync input should also work with other systems but I didn't test any other than this

[Lastcallhall]

That's pretty cool. If you can get a handle on this, you could pull off some interesting effects, one would think.

[Jorge Nuno]

Yeah, however I dont have any clue on how would I put 2 blast processor boards inside a single shell with 2 game slots

[Kamahl]

Should have been posted in blast processing , But this is pretty interesting.
Sega should have abused this somehow.

[Oerg866]

I believe this technology is called "genlock", and people paid big money to get this feature on their Amiga computers. Genlock cards were popular albeit expensive, and the Sega has this out of the box.

Take that, Amiga =P

Nice job jorge, now go build a computer out of that thing >

Cheers!

[Jorge Nuno]

I said in the OP tht I read about the VDP video overlay thing in genvdp.txt but it's not mentioned there... Where did I read this from?

O_o

[Chilly Willy]

I believe this technology is called "genlock", and people paid big money to get this feature on their Amiga computers. Genlock cards were popular albeit expensive, and the Sega has this out of the box.

Take that, Amiga =P

Nice job jorge, now go build a computer out of that thing >

Cheers!

Uh - genlocking was built into the Amiga from the very beginning. Because of that, genlocks for the Amiga were super cheap. While the Amiga itself was more expensive than a console, it was about the same price as most computers, or a bit cheaper, depending on the computer in question. It was certainly MUCH cheaper than a Mac. I had a genlock I got for my Amiga 500... I think I paid like $60 for it. They had more expensive models, but they were for professionals.

[Sik]

Well, the Amiga probably had genlocking built-in (good luck forcing video hardware to genlock if it doesn't come with the ability already!). I think Oerg meant the cards that routed the proper signals to allow the genlocking... (which also means they were overpriced, but eh, people are stupid!)

[Chilly Willy]

Well, the Amiga probably had genlocking built-in (good luck forcing video hardware to genlock if it doesn't come with the ability already!). I think Oerg meant the cards that routed the proper signals to allow the genlocking... (which also means they were overpriced, but eh, people are stupid!)

I did most of my early commercial work on the Amiga, and I can tell you for a fact that the Amiga DID have genlocking built-in. No "probably" about it.

Not sure what Oerg was talking about... maybe he can elucidate on that.