japanese sega mega drive with two pcbs

There is a similar PCB on european megacd2 (at least the one i have, a pcb with few 74x counters)...
Like a fix to a hardware bug discovered later like retro said...

Yeah, we want more details about the chips

 

http://i62.photobucket.com/albums/h113/goregrime/DSCN0182.jpg

http://i62.photobucket.com/albums/h113/goregrime/DSCN0190.jpg

 

They're just 7400 series logic chips.

 

Looks like it's just a kludge fix for the clock.

 

Maybe a fix for some 68k clone ? I notice that the cpu is not a Toshiba or Motorola 68k...

 

Your right it's a Signetics 68000 and I know they do have problems with the clock so the board is probably to make sure the clock signal is accurate.

 

My Samsung Mega Drive had Gold Star chips in it!

Yakumo

 

I m not surprised..their car radios/cassette decks were shit.

 

thanks for all the replies, so its a fix for the 68k processor? cool.
would this have been an earlier or later version, is there some way i can find out when it was made?

 

Oh, I missed the new pics. Much clearer! :thumbsup:

Well, you've got a 53.683MHZ (?) oscillator, 2 synchronous 4-bit counters and a dual D-type positive edge-triggered flip-flop.

The mod seems to be going to IC8, which is the 315-5313. Are there any other connections under the PCB or not? The circuit diagram suggests that there should be a 53.634165 MHz oscillator on pin 52 (MCLK) of IC8. It doesn't really look like it is anywhere near!

Here's the diagram by the way:

http://emu-docs.org/Genesis/mega2.png

 

This is a real MD for sure not a clone... I really want to know its VAx (board revision), I cannot see it on any pics. It must be a VA0, VA1 or VA2.

 

This is just a guess but it might be a counter that resets the cpu after a set ammount of time.