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Hi All,

This is pretty much a newbie question, but I haven't really found a proper answer to it yet:

What kind of accessories were released for the expansion port? I assume this is the connection accessed from behind the sliding cover at the bottom of the SMS Mark I. Is there any reason why my model has a plastic blanking panel covering the connection? It would seem pretty redundant to manufacture a console specifically with a sliding cover that had nothing behind it. Or was this where you could keep your secret jelly bean stash?

Thanks,

dodginess

Nothing was ever made for it. It's actually the same as a cartridge slot, except of course it's backwards from that; if you make an adaptor you can plug a cartridge in there and it'll work. It costs almost nothing to make that kind of edge connector, and it left options for things like the never-released-maybe-never-existed disk drive add-on. The plastic cover just avoids kids sticking metal things in there and destroying the system.

The expansion port was present on the Japanese SMS and presumably the port and sliding door on the export SMS1's is a carryover from the Japanese design. It may not have been decided until late in the export SMS's development cycle that the expansion port would not be supported outside Japan, so the board and case was kept intact except for the tabs to block it.

As it turned out, the expansion port was not used in Japan, either. At one point it is believed they were planning on a computer expansion for the SMS.

The expansion port, however, is functional on non-Japanese Master System. It is attached to the memory bus of the SMS and operates like a second cartrdige slot. There is potential for it to be used in homebrew electronics projects, such as cartridge dumpers and an i/o path to a computer.

Just to clarify, the original SMS's with the red highlights and the angular design is usually referred to an "SMS 1". The Mark II was an expanded SG-1000 and the Mark III was the precedessor to the SMS, though fully compatible with SMS software. I've seen the SG-1000 referred to as the Mark I but I don't believe it was actually referred to as such when it was in production.

My Brazilian SMS II (Master System and Master System II in Brazili are the same, with different Built in games) have this port too. But I never used it...

This remembers me when I was a kid, I wasted a lot of time thinking about that expansion port, dreaming for something like a SEGA CD :-)

It was really cool.

PD

CD Drive 4 the SMS...

It's all possible my dears...

Just a matter of time and patience we can design lots of those inventions 4 the machine...

Cheers

That CD thingy that have for the Atari 2600 is sweet, if they had one for the SMS, I'd buy one, granted it wasn't too expensive.

I'm sure a CD player for the SMS is perfectly possible, but is it worth the effort? ;)

Now, what would be *really* handy is a hard drive for my Dreamcast! Any takers?

I know this is an old post, but I find it funny that nobody made mention of the fact that there were expansion port accessories in Japan, such as the keyboard attachment and I believe the FM Sound Unit as well, but they were configured for the prior expansion port standard which was in in use on the SG-1000, Othello Multivision, Mark II, and Mark III. Possibly the Dina 2 in 1 as well.

You wouldn't be able to attach these to a Master System straight out of the box, but I bet with an adapter you could.

The King of the Mods wrote

Possibly the Dina 2 in 1 as well

The DINA has its own weird expansion port that isn't compatible with either ColecoVision or SG-1000 accessories.

I've been playing with the expansion port on a Japanese SMS using a BackBit expansion adapter recently and I found some interesting things.

There are a handful of games that will not run from the expansion port without patching them. Around 17 games in my testing. Some common games too like Outrun and Rastan will not natively run through that port without the roms being patched.

Author	Message
dodginess Joined: 21 Mar 2005 Posts: 51 Location: United Kingdom	Expansion port question Posted: Thu Oct 27, 2005 10:44 pm
	Hi All, This is pretty much a newbie question, but I haven't really found a proper answer to it yet: What kind of accessories were released for the expansion port? I assume this is the connection accessed from behind the sliding cover at the bottom of the SMS Mark I. Is there any reason why my model has a plastic blanking panel covering the connection? It would seem pretty redundant to manufacture a console specifically with a sliding cover that had nothing behind it. Or was this where you could keep your secret jelly bean stash? Thanks, dodginess

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14745 Location: London	Posted: Thu Oct 27, 2005 11:36 pm
	Nothing was ever made for it. It's actually the same as a cartridge slot, except of course it's backwards from that; if you make an adaptor you can plug a cartridge in there and it'll work. It costs almost nothing to make that kind of edge connector, and it left options for things like the never-released-maybe-never-existed disk drive add-on. The plastic cover just avoids kids sticking metal things in there and destroying the system.

Heliophobe Site Admin Joined: 25 Oct 1999 Posts: 2029 Location: Monterey, California	Posted: Thu Oct 27, 2005 11:52 pm
	The expansion port was present on the Japanese SMS and presumably the port and sliding door on the export SMS1's is a carryover from the Japanese design. It may not have been decided until late in the export SMS's development cycle that the expansion port would not be supported outside Japan, so the board and case was kept intact except for the tabs to block it. As it turned out, the expansion port was not used in Japan, either. At one point it is believed they were planning on a computer expansion for the SMS. The expansion port, however, is functional on non-Japanese Master System. It is attached to the memory bus of the SMS and operates like a second cartrdige slot. There is potential for it to be used in homebrew electronics projects, such as cartridge dumpers and an i/o path to a computer. Just to clarify, the original SMS's with the red highlights and the angular design is usually referred to an "SMS 1". The Mark II was an expanded SG-1000 and the Mark III was the precedessor to the SMS, though fully compatible with SMS software. I've seen the SG-1000 referred to as the Mark I but I don't believe it was actually referred to as such when it was in production.

superbarra Joined: 28 Oct 2005 Posts: 1	Posted: Fri Oct 28, 2005 12:18 pm
superbarra Joined: 28 Oct 2005 Posts: 1	My Brazilian SMS II (Master System and Master System II in Brazili are the same, with different Built in games) have this port too. But I never used it...

PrOfUnD Darkness Joined: 29 Jun 1999 Posts: 383 Location: Brazil	Posted: Fri Oct 28, 2005 7:29 pm
	This remembers me when I was a kid, I wasted a lot of time thinking about that expansion port, dreaming for something like a SEGA CD :-) It was really cool. PD

unoesis Guest	Posted: Sun Oct 30, 2005 1:28 am
unoesis Guest	CD Drive 4 the SMS... It's all possible my dears... Just a matter of time and patience we can design lots of those inventions 4 the machine... Cheers

das Joined: 02 Oct 2005 Posts: 19	Posted: Sun Oct 30, 2005 3:58 am
das Joined: 02 Oct 2005 Posts: 19	That CD thingy that have for the Atari 2600 is sweet, if they had one for the SMS, I'd buy one, granted it wasn't too expensive.

dodginess Joined: 21 Mar 2005 Posts: 51 Location: United Kingdom	Posted: Sun Oct 30, 2005 11:30 pm
	I'm sure a CD player for the SMS is perfectly possible, but is it worth the effort? ;) Now, what would be really handy is a hard drive for my Dreamcast! Any takers?

The King of the Mods Joined: 24 Aug 2014 Posts: 53	Posted: Fri Dec 15, 2023 11:44 pm
The King of the Mods Joined: 24 Aug 2014 Posts: 53	I know this is an old post, but I find it funny that nobody made mention of the fact that there were expansion port accessories in Japan, such as the keyboard attachment and I believe the FM Sound Unit as well, but they were configured for the prior expansion port standard which was in in use on the SG-1000, Othello Multivision, Mark II, and Mark III. Possibly the Dina 2 in 1 as well. You wouldn't be able to attach these to a Master System straight out of the box, but I bet with an adapter you could.

ApolloBoy Joined: 30 Jan 2007 Posts: 317 Location: San Jose, CA	Posted: Sun Dec 17, 2023 6:42 pm
	The King of the Mods wrote Possibly the Dina 2 in 1 as well The DINA has its own weird expansion port that isn't compatible with either ColecoVision or SG-1000 accessories.

eightbit Joined: 12 Aug 2019 Posts: 11	Posted: Sun Jan 28, 2024 3:51 am
eightbit Joined: 12 Aug 2019 Posts: 11	I've been playing with the expansion port on a Japanese SMS using a BackBit expansion adapter recently and I found some interesting things. There are a handful of games that will not run from the expansion port without patching them. Around 17 games in my testing. Some common games too like Outrun and Rastan will not natively run through that port without the roms being patched.

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