Author Topic: Krikzz could you update the OS to make it work thru expansion port, please?  (Read 4977 times)

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Offline ivan

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Hi,
I have a japanese Master System and I use Master ED connected through expansion port.
The problem is that some games refuses to work and I'm getting black screen.
The strange thing is that original games works perfectly, so I think that Master ED is disabling the rear port.
List of some games that works using original cartridge but not working on MED (Expansion Port).

- Cyborg Hunter
- Double Dragon
- Kenseiden
- Outrun
- Vigilante

I know that there is a hardware mod to make it work but I don't want to modify my system.
I assume that this is an easy OS update. ;D
Thanks

Offline phoenixdownita

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Not so fast, the SW (games) is responsible for messing up the CS (chip select) that the SMS uses to decide where to read the game data from.
The Master System has 3 hardware lines (CS signals) to select where to read the ROM from (cart, card and expansion) and they are controlled by SW on a specific port. The SMS stores where it found the boot at that port (http://www.smspower.org/Development/Port3E).
The same port is also shared with other bit setting so most SW was assuming it didn't need to preserve the bits that indicate the boot device.
If the game code hardcodes the value there it will switch the CS from exp to cart (the most common case) and fail.

An adapter was being made for Jap to Western SMS cart port not sure who sells it these days (a few years back I helped finishing the first pin mapping to make such an adapter possible and with almost 100% compatibility).
Back to the hotspot location a few games were actually patched to block the bad behavior but I don't have the list handy.

So an OS fix is not possible, actually the OS was fixed from v5 to v6-test to support JP SMS, then it got into v7 onward (the fix is so the MasterED OS itself does not mess up with that port and preserves whatever the SMS puts there during boot), before that it was much worse (can't remember if it could get past loading the OS or if it crashed after loading a game but before starting). Finally there's a couple of US games that do not work on Jap SMS because of the FM chip (and there's no way to disable aside patching the games).
« Last Edit: December 05, 2017, 07:41 AM by phoenixdownita »

Offline LDigital

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Late to the discussion but you can mod your Japanese sms to think that the expansion port is the cart slot. This will clear up nearly all compatibility issues

Here is a pic of mine

I take no responsibility for anyone else’s machine if you follow this guide.

Cut the one trace on the left

Attach a wire between the 2 points like I have, there is even a convenient hole to put the wires through

Job done, your expansion port now functions as the cart slot and is everdrive ready

Offline FeverDrive

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Late to the discussion but you can mod your Japanese sms to think that the expansion port is the cart slot. This will clear up nearly all compatibility issues

Well...

I know that there is a hardware mod to make it work but I don't want to modify my system.
I assume that this is an easy OS update. ;D
Thanks
WELCO
METOT
HENEX
TLEVEL

Offline Nanasato

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It is very necessary for me to be looking.

Offline J-E

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at home, my everdrive works perfectly on the rear port of the japanese SMS.
except for the games cited above.