Sega Megadrive Address Checker: Formerly "Unknown PCB"

First of all thank you! I will make some pictures within two weeks. I'm a little bit busy right now. I have to fix this adapter (some pins are broken) and prepare a sega megadrive for it.

 

Success!

I finally tested the card and it works. I desoldered the CPU of a sega mega drive 1 and added one of the sockets. Than i plugged the card in.

The game starts as usual. When you press SW2 the game will freeze and the display shows you the current address (LED: ADD). If you press SW1 the display shows you the data of this address (LED: DAT). If you press SW2 again th display shows you the instruction pointer (LED: PC). If you press both SW1+2 the game continues.

It's not necessary to plug in a power supply, but it works too.

I don't have a clue what the dip-switches (SW3) are for.

 

Probably something to do with the purpose of the device--to break on illegal memory access.

 

I too would enjoy some electronics pornography.

 

[video=youtube_share;wavkqOuRCBQ]http://youtu.be/wavkqOuRCBQ[/video]

 

Neat. You should try some unlicensed games that access illegal/unused memory to see what happen.

 

Which game could I use for this test? Any idea? :shrug:

 

I used my Everdrive and Tekken 3 for testing. It seems that the Everdrive is using an illegal operation to start the loaded rom. Tekken 3 stops working right before the fight.

I think the dip-switches of SW3 have the following tasks:
1000 -> Freeze-Mode (see my Post #22)
0100 -> Debug-Mode (detects illegal operations)
0010 -> ???
0001 -> ???

[video=youtube_share;m-zz_n5Rs7M]http://youtu.be/m-zz_n5Rs7M[/video]

 

Illegal operation sounds like you mean illegal opcode (the operation part of a processor instruction) instead of illegal memory access. It's very unlikely this can catch those.

 

I know UMK 3 hack is accessing illegal area and triggers Address Error exceptions (word access to odd adress) but I don't know if it can be flashed on Everdrive MD (it's 10 MB)

Sonic Cracker beta also does weird stuff on the start sceen

Everdrive OS might itself access unused memory area for its own hardware (internal registers) as well.

 

Thanks.
I was not able to test the UMK hack, but Sonic Crackers was a hit.

BTW: I meant 'illegal memory access' not opcode!

 

Here are all of my hires pictures - i hope you like it:

 

Video 3:
[video=youtube_share;RcOV9Uk9pRQ]http://youtu.be/RcOV9Uk9pRQ[/video]

 

Video 4:
[video=youtube_share;_c0u36AYfwM]http://youtu.be/_c0u36AYfwM[/video]

 

Video 5:
[video=youtube_share;29K0fIsW3ro]http://youtu.be/29K0fIsW3ro[/video]

 

epic

 

Do you mind me asking what are those other mods done to the system it is it in fact a devkit ??

 

Neat! I wonder where such interesting dev tools can be found for cheap.