When I was designing my SMS (non-Japanese) to Megadrive/Genesis cartridge adapter, I learned that the Japanese version of this console used a different connector (44 pins instead of 50).
So I decided to also design an adapter for Japanese cartridges. The schematics for this new adapter
are presented here.
Supports Sega MarkIII/Japanese Master system cartridges.
Tested on Mega Drive I and II (North-american and Japanese systems).
.STL files available to print your own enclosure.
Not compatible with Genesis 3
Here are a few pictures of the resulting adapter:
Japanese Phantasy Star
With enclosure v1
アリサはいきていますよ。 Alisa is alive. The adapter too!
Most of the time, installing the adapter (in the correct direction),
inserting the cartridge and applying power is all that is needed. But
there can be some issues depending on the game:
1) Controller problems
Some games won't work properly using Megadrive controllers. A solution
is to Master System controllers instead, or to build a special adapter.
2) Start-up problems
When an SMS game is run on a Megadrive console, there is no bios
to run before the game. The CPU executes the game right from the
start. This can be a problem for games which rely on intialization
normally performed by the bios, in particular setting up the stack
(I learned about this thanks to reference #5)
A quick workaround to this is to first run SMS game that
does not have this problem, turn off the power, insert the
non-starting game and reapply power. Now the game should start.
This is because even following the power cycle, the stack pointer
register bits haven not faded away yet and are still at the
last value used!
February 2015: The above manipulations can be avoided by adding a stack
My collection of japanese titles is not very large, but here
are those that are tested:
Megadrive controller (1)
Stack pointer (2)
星をさがして…(Hoshi wo sagashite)
ソロモンの鍵・王女リヒタの涙(Solomon no Kagi - Oujo Rihita no Namida)
ファンタジーゾーンII オパオパの涙(FANTASY ZONE II The tears of OPA OPA)
アレックスキッドのミラクルワールド(Alex Kidd no Miracle World)
No. Use SMS controllers.
赤い光弾 ジリオン(Red photon zillion)
トライフォーメーション(Zillion II: The Tri-Formation)
孔雀王(kujaku ou / Spellcaster)
No. Use SMS controllers.
Does not work because it is an SG-1000 game.
Gamboy game: Super columns
Does not work.
Please report if you try other games. I'd like to list them here.
 Games compatible with the Sega SG-1000/SC-3000 are not supported. Only Mark-III exclusive (マークIII専用) games will work.  The Gamboy is a Korean version of the Sega Master System.
It would seem that most GamBoy games are in fact SG-1000 games. But I'm told one possible exception is Super Boy 4.
Here is the schematic. I used my previous adapter project as a base and consulted
the same références.
Components marked "NP":
For this adapter too, I placed a few 0 ohm resistors for easy rewiring of selected signals,
just in case. (In the schematic, resistors maked as "NP" are not to be normally installed.
Errata: I made a mistake on the CE (Chip Enable) signal wiring. On the SMS side,
it should be wired to pin 19 (MREQ) instead of pin 17. A small piece of wire must therefore
be installed between those two pins, otherwise nothing works. This fix is shown in red in
the schematic and pictured on the right.
I designed and had a PCB built specifically for this project. Basing my adapter on a rewired SMD cartridge would have taken too much time. I kept height of the PCB low as I did not wish to have the SMS cartridge hanging too high when using the adapter. (The MarkIII cartridge is already tall enough!)
Here is the PCB as it was built. It is available, in kit or ready to use, in my
The MarkIII cartridge connector has 44 pins with a .125" (3.18mm) pitch. The one I used
is Edac Inc. p/n: 346-044-520-202. As it was meant for through-hole soldering, installing
it on a PCB edge like I do here requires bending the pins..
I designed and printed a casing for the adapter. Here is the .STL file should you
want to print one: sms2smd_m3_casing.zip
February 2015: I discovered that the above enclosure is not usable with the Megadrive 1!.
I happens that what was a design I was satisfied with on-screen ends up
being a bit disappointing in reality. This was the case with the
first enclosure I show above. After reworking it a bit, here is
February 2015: I confirm that this version of the enclosure works without problem with the Megadrive 1 too.
There are a few games that will not work properly with Genesis/Megadrive controllers. A solution is to
use SMS controllers, but it is also possible to build this compatibility adapter. The idea is to keep
the SELECT signal on the controller side high through a resistor (100kΩ).
I don't personally own any games where this adapter is necessary, so I have not built one.
But ishiyakazuo who suggested this solution says it works great.
Pictures and pinouts for a SMS cartridge. This was of great use to double-check that I made no mistake with the connector orientation. There's also information on the connector used on Japanese systems which should be useful if I make a Japanese version of this adapter.
A very interesting discussion which begins with technical information on the custom chip Sega uses in it's own adapter (It looks like this chip initializes the stack, required for some games). Farther in the discussion, there is a schematic (sega2sms.png) a bit difficult to follow, but useful, and matching the wiring table above in reference 1
I cannot be held responsible for any damages that could occur to you
or your equipment while following the procedures present on this page.
Also, I GIVE ABSOLUTELY NO WARRANTY on the correctness and usability
of the informations on this page. Please note, however, that the procedures
above have worked in my case without any damages or problems.