Genesis Question

I just got a Genesis today. It's the large model one, with the headphone jack and volume controls. I opened it up in hopes of overclocking and found something odd.

I can't find the region jumpers on it, and the PCB is much different than anything I've ever seen.

Here are some pictures:




Any ideas about this revision?

 

Might be the 1991-era system that came with a Sonic 1 pack-in.

 

Oh well, I just swapped it for another one, and I see through the side its got all the JP jumpers, so time to crack it open.

 

Interesting PCB, it has a 315-XXXX chip just like a MD/GEN2 yet still has the original Z80! Bizzare!

 

Well.. I crack this one open and I find something else..



Its under the 68000.

 

here is a better picture:

 

MegaDrive 1s with square 68000s and normal Z80s are rather common. They also have just one regulator .. they're like a version of the MD2, in the MD1 casing. They retain the headphone jack and volume control, however..

I call this the 'MD1.5' revision. About 6% of all machines are this type.

 

Heh, how did you know that?

 

Epicenter, if you were a Sega tech you'd call it a VA7 board (one of the later life boards)