Mega PC

[Sifter]

Hi all, my first post, hope this is the right place for it. This might well be quite tricky - basically, I've got hold of an old Amstrad Mega PC. This is quite a rare PC, and it's a 386SX PC with a Megadrive inside it. THe Megadrive itself is a one circuit board affair that connects to the ISA slot on the PC's motherboard. There's also a small 20pin ribbon connection running from the Mega Drive circuit board to the the motherboard.

I've take the Megadrive board out of the Amstrad PC, as the Amstrad is knackered and I want the Megadrive in a more modern PC. So I've got a Pentium 4 motherboard with some ISA slots and rigged it all up. Surpisingly, it works - I get sound from the Megadrive when I put in a cartridge, but not video. I'm guessing the Megadrive board only takes power from the ISA slot, and that the video is outputted via the small ribbon connection. So my question is, does anyone know how I can connect the Megadrive board to a monitor? I guess I need a pinout diagram of the 20pin ribbon connection, or a way of finding out which is which, so I can wire it up to a monitor.....

Any help very gratefully received

Thanks in advance..................  

[NFG]

That's a pretty fascinating concept, I didn't realize the MD part was so modular.  The pinout for the connector is unknown, but it should be easy to figure out what's what with a little effort and a multimeter.  Track down signal from the video output back to however it gets to the ribbon cable.  Presto, there's your video line.  Might be better off to hack the system for RGB tho, see if there's a Sony CXA video encoder there somewhere, that'll be a great starting point.

[ido8bit]

Wasn't there also a Japanese machine that was a PC and Megadrive in one?

I had one of these cards once, but I gave up trying to get it to work.  Though I was missing the cable that carries the cartridge and controller connectors.  The thought of having to trace all those connections and then still have to solve the video problem was more than I could be bothered with.  

There is no real way to use this card in any normal PC.  The 20 pin ribbon cable from the card goes to a connector on the motherboard and is part of the motherboard's onboard VGA, similiar to the feature connector on old video cards, but not the same.  

This cable carries the RGB output from the Megadrive.  I don't remember what the other pins are for.   When the MegaPC is being used as a Megadrive the RGB video from the Megadrive is passed directly to the monitor.  The PC does nothing to it, it is not line doubled.  It goes in and comes out with 15KHz sync.

A standard VGA monitor doesn't handle 15KHz sync.  The MegaPC was supplied with a multisync monitor that does.  If you used a standard VGA monitor on the MegaPC it would only work when using the PC, not the Megadrive.

If you really want to get this card running your best option is fix the 386SX it came out of.  If it's the monitor that has died you'll need to replace it with a multisync monitor, such as an NEC multisync (original, 2, 2+ or 3D).  

BTW:  The card has a bus connector on it for a MegaCD, I guess they were planning MegaCD add-on (with PC CD-ROM support?) that was cancelled when the MegaCD was a flop.  

[FaZyCrUcK]

I have one of those somewhere.. mine still works as far as I remember, hehe. Never opened it tho, in my loft I think.

Andy

[Segasonicfan]

the japanese version was called the Teradrive...I'm really looking for either version....hard to come by though, anybody want to trade me one? ;-)  Sounds like an interesting mod youre doing....good luck ;-)

-Segasonicfan