10 replies to this topic

[Tempest]

Has anyone tried to build a Sega Master System multicart? I love the SMS, but trying to get all those overseas games (which is 70% of the library) is tough. I was cuious if it was indeed possible to make a multi-cart and how many games it could hold.

Tempest

[joeybastard]

Ooohhh I'd want one of those. I love my SMS but very very rarely come across games in the wild.

[MegaManFan]

I have a half-dozen SMS games on my tradelist right now Joey, and the Gamers on 72nd has two-or-three dozen loose games right now (the ones on my list are all boxed except Phantasy Star).

[Susuwatari]

SMS multicart is actually easier than 2600 multicart since you won't need to add inverter or rearrainge a few lines. If there's one drawback, some of the larger SMS games wouldn't work well as multicart. And 8MB EPROM cost almost as much as getting the actual SMS game CIB. For smaller SMS games, it can be done with DIP switch to toggle higher address lines.

When I get my 4MB EPROM in, I'm going to cook up an 8-in-1 multicart using 8x 4Mega games. The EPROM would be selected by toggling /OE lines. I'm planning to use 3 pos DIP swith (4 actually, the extra would be unused), tie it to a7442 4 bit to 10 line deconder (since 4th bit won't be used, line 8 and 9 won't be used either), and then through hex inverters. (since EPROM OE line is active low and I'd want only one EPROM enabled)l. Then all I'd have to do is stack up the EPROM as all lines except /OE would be the same.

Fior the moment, none of the 4 Mega games I'm using will use battery backup. I haven't figured out how to properly bankswitch the SRAM chip to match the EPROM bank. Plus there's very few games that actually uses SRAM for save games (Golden Axe Warrior, Monopoly, Ultima 4, and Phantasy Star are all I know of)

Here's a link for installing 1MB EPROM (128K or 1 Mega game) http://www.smspower....od/cartmod.html
Here's a link showing more details about the few mapper chips Sega used so you could work on multicart: http://www.smspower....agingChips.html

[DeV0]

I have the official mega games cart that has 4 games on it, so at least that much is possible.

[SteveW]

How about a device like a CuttleCart/Intellicart, where you could plug the cartridge into a computer with a serial cable, and just load binaries into it?

[Susuwatari]

Something similiar had been done: http://www.smspower.org/smsreader/

It uses SRAM and quickly loads one game to the SRAM cart and then you can plug it in and play to your heart's content. Crude but it works well. The reader can also read and write to saved games on the cart so you could transfer your saved game between the PC for emulator and the SMS.

Note, this o0ne covers up to 256K SRAM cart so 4 Mega games won't work. But if you look on the 256K SRAM cart and check the docs for the mapper chips elsewhere on S8 dev page, you could figure out how to make 4x 1Mbit SRAM setup work I don't know if the SMS Reader software will write 4 Mega game or not, you'd have to ask that You ciould use the S8 Sega dev board fior this kind of question here at http://www.smspower....rum/index.shtml

[holygrailvideogames.com]

If you do find someone making an SMS multicart, let me know. I would be very interested.

Do you know if anyone makes an Genesis multicart? It would be great to have a Genesis multicart to use with a Nomad.

[chrisbid]

sort of on the same topic but not really, ive seen a few tech demos and really simple homebrew games on the SMS, since carts seem to be expensive to put together, and there really isnt that many common SMS games to carve up into homebrew, would the card slot be a viable option? ive seen some of the turbo graphx and lynx games from good deal games where the chips are glued onto the open end of the card, i would think the same method could work well for the SMS. Sure, the limit is 128k, but i doubt there are any homebrew projects at the moment that need any more.

i guess this question is better suited for the smspower forum, but i hate those kinds of message boards that force you to click on each individual reply

[Susuwatari]

chrisbid said:

sort of on the same topic but not really, ive seen a few tech demos and really simple homebrew games on the SMS, since carts seem to be expensive to put together, and there really isnt that many common SMS games to carve up into homebrew, would the card slot be a viable option?  ive seen some of the turbo graphx and lynx games from good deal games where the chips are glued onto the open end of the card, i would think the same method could work well for the SMS.  Sure, the limit is 128k, but i doubt there are any homebrew projects at the moment that need any more.  

The card slot can only access a maximum of 32K since the extra address line (A15) aren't available. Even if you tried to hack a larger game to fit on card, games expects to be able to access 64K section at a time. You'd have to reprogram the game completely so it's bankswirtched in 32K section rather than 64K. A ittle messy.

It's still easier to use the card slot. Card slot uses standard 25/50 pin card edge connector with 0.10" spacing and it's readily available from various online electronics supplier. And because SMS games 64K and smaller can be directly accessed, you could just drop in an EPROM, no extra circuitry at all.

Mega games (1Mbit or 128K) and larger requires bankswitching to handle larger games but its design is ell documented and it's possible to build your own bankswitching circuit with something like a PAL or whatever. It's basically a bankswitch watchdog that monitors address line and data lines and controls A14 to A18 lines to the ROM chip.

Quote

i guess this question is better suited for the smspower forum, but i hate those kinds of message boards that force you to click on each individual reply

I don't like those style either but it's full of people that knows every diode inside and out of SMS and Game Gear. The only one question no one has been able to answer yet is the pinout of the Game Gear LCD display. The LCD had to be partially NTSC compatible since GG and SMS are virtually the same with minior differences. My best guess is 3x 4bit RGB input (12 bit total) plus composite synch.

[chrisbid]

sorry i got the numbers wrong, im not much of a tech head, but i love my master system, and seeing how great the atari and coleco homebrew scenes are, id love to see a master system homebrew scene, with games i can play on my actual system