Oh btw guys I've made some PCBs for blank SMS carts - I might have a few left over - and I'm happy to share the PCB file etc if anyone is interested.

I'm not very pro destroying old games - call me a hoarder if you want to...

little-scale wrote:

..share the PCB file etc if anyone is interested....

<RAISING HAND> Could I get a copy of your PCB file, please? I feel the same about crack'n open a classic cart, unless we're talking about Atari's ET :-)

LOL yeah fuck ET. wink

Good call.

Look, I have the feeling that the file is on a HDD at home somewhere, when I find it I'll def. post it! big_smile

Cool, thanks

If you wana sell a pcb with the eprom that would be awesome. Otherwise would the master everdrive work, so that i could update the rom?

Actually if the everdrive works, i would prefer this method so that custom samples could be put in.

Yes the everdrive / any method of using a custom ROM on a sega would work.

Bumping this for a little info.
Been gathering parts to put an SMSM together on a GG. Got an ebay GG: turns out it needed a little more work then the seller thought. So Ive been on a GG crash course, learning all 'bout the bad caps. Also got a World Grand Prix cart, and started learning 'bout the diff. board versions, Brown vs White boards, and the Sega mappers. The cart that I received has a 315-5208 mapper and a 831000 MPR.
So I believe from my searches, that the footprints for the 831001 is the same as the 831000 ROM, the only difference is the internal mapping logic on the '1001.
If I remove the mapper chip, I think I can jumper a few pins to have the same functionality as the 171-5519 cart board. Now I was also thinking that if I leave the mapper in place, I could use a 32 pin socket (found a How-To Flash Cart for this) and either use a 27C256 or a 27C010. Of course the 1MBit EEPROM would have to be padded for the SMSM firmware, but the mod could be a useful 1Mbit flash cart for developing.
So a few questions for anyone:
!. Am I correct about the 831000 and 831001? The only difference is the internal mapping logic in the '1001? I've found pin-outs for the mapper and the 831001, but not one for the 831000 yet.
2. If I leave the '5208 mapper on the board, will a 27c256 operate? Plugging it into the lower end of a 32pin socket looks fine pin-wise. The mapper seems to map 8 16K pages, and a 27c256 would occupy the two lowest pages, so if the firmware is contained within the first page we don't need any page crossing code for the mapper?
3. What is the size of the SMSM code block? I know it's in a 32K hex file, but is there allot of padding to fill the 32K? Is it <16K?
I'll post how it works out for anyone that's interested.

EDIT- after re-reading some reference sources, the mapper addresses one page at 0x0000-0x3FFFF and bank switches 7 other 16K banks at 0x8000-0xBFFF, controlled by a reg mapped at 0xFFFF.  For a total of 128K. -EDIT

Last edited by yogi (February 20, 2013 4:35 am)

The firmware is tiny! Not sure, but i'd say easily less than 16k...

Can't help you with the rest, though it's weird that World Grand Prix has a mapper at all (I thought it didn't need one??)

Here's a pretty handy guide for replacing capacitors on the game gear
http://members.optusnet.com.au/eviltim/ … epair.html

Thanks Seb, I was thinking the softs had a small code footprint, from looking over the source file.
If my research is correct, the 831001s are 128K x 8 devices, having internal mapping logic, on 'Brown' phenolic boards. It seems that other, (newer??) carts were produced with 831000s, 256K x 8 devices with a separate mapper chip, on 'White' FR4 boards. But the board material 'test' is not 100%, some of the 2MBit and 4MBit carts are on phenolic boards also.
If I understand correctly, to bank switch the 0x8000-0xBFFF page, you need a write to 0xFFFF with D2:0 holding the A16:14 bits. http://cgfm2.emuviews.com/txt/smsmap.txt
and here
http://www.smspower.org/Development/SMSPagingChips

EDIT-: Just noticed that the Charles MacDonald txt, the first link, lists the '1001 as a 128K device and the '5208 mapper is for 128K devices. Where as the second link, @ SMS Power, it notes the 831000 as a 256K device, but I think this is in error, and the 831000 is in fact a 128K device. -EDIT

I'm guessing that the game code is probably the same for both WGP carts, but don't know if it uses mapping; could be that the page banking calls are just handled by a separate chip rather then the internal logic, or it's totally contained in the 0x0000-0x3FFF page. My guess is: cheaper inventory costs, even with two chips on a cart. But hey, I have an NTSC cart, whereas you used a PAL, so maybe that is the difference?!?!
I've got a ThunderBlades cart on a 'brown' board coming, don't know what I'll have but it was worth a shot.
I'll prob pull both chips off the WGP board and socket it. Then I can test with jumpers or the mapper chip with the 27c256.
But first I have to finish re-capping the GG, got the screen and contrast working. but it's still not booting right; hangs right after the 'Lic' screen, no "Sega!".
Got a few more caps to replace before I'll know if I'm done or if I need to dig deeper. tongue Either that or the GearMaster isn't working right; was NOS off ebay, boxed, so I'm hoping it's fine.<Fingers crossed>

Last edited by yogi (February 20, 2013 4:25 am)

Saskrotch wrote:

Here's a pretty handy guide for replacing capacitors on the game gear
http://members.optusnet.com.au/eviltim/ … epair.html

Thanks, Saskrotch. I've seen that page, it's very good. There is a video also, I guess I didn't bookmark it, that was very helpful. There are allot of different boards versions but most guides are general enough and the SMD 'litics are easy to read, so it's not too bad.

Well after finishing the re-capping, The GG still wouldn't load a SMS cart.. So after trolling Ebay again, another GG with screen problems (but not too bad) came with a Sonic cart; got another SMS cart also, Thunder Blades ( has a larger 832011 ROM, 32 pin. But the board will accommodate a 27256 just fine!). The good news is the re-capping worked wonders, the sound out is working great!
So I confirmed that both GGs boot fine with the Sonic GG cart and neither boot with either SMS cart! X(  SO, the GearMaster is @ fault!! In a sealed package when my son got it for me;  WTF?!?
I'll have to test it. I'm guessing there may be a problem with the GG/SMS pin looping, remember reading 'bout an issue like that. Or there could be a connection issue. Not much else going on inside it. We'll see.

How difficult do you think it would be to solder an EPROM or a cart directly to the GG?

I mean I don't want to be the guy saying something obvious and dumb if it hasn't been overlooked but...

SMSM doesn't really have a bootup screen or anything, it's just a black screen. I hope this got mentioned at some point.

little-scale wrote:

How difficult do you think it would be to solder an EPROM or a cart directly to the GG?

EDIT- To your point LittleScale, there is enough room in the case for an EPROM, but access to the solder points on the mobo would be a problem. The easiest  would be at the cart connector, but would have to get at the 'back' side, that faces the LCD and run the wires to the top side without damage to the LCD wiring. Or remove the cart connector all together and wire from there, but would have to move the LCD out of position during that work also. On the other hand, don't really need the LCD for this app, so I'll take a closer look at a mod like that -EDIT

I did see a GG Dev cart at SMSPower that added jumpers from a GG cart, to a outboard EEPROM dip socket board. Seemed like a easy enough process. The GG cart being all SMD, makes it hard to use dip chips.

I was planning to follow that guide for my trouble shooting on the GearMaster (which is basically the same thing). In the end, once I get things working with the GearMaster, I'll build up the 'homebrew cart'. Seeing as I ended up getting a second GG. Stereo!! smile

@ Saskrotch. I haven't modded the SMS carts yet, wanted to verify everything works with stock parts first. But yea good point. The weird thing is: with the GG cart you get a 'Lic' screen then it blanks, half a sec later the 'SEGA' and the game starts. With the adapter and SMS carts, you get the 'lic' screen, blanks like normal, then nothing. But the text is different, a little larger font. As far as I can tell there isn't a bios in either GG, so is the 'Lic' text being read off the ROM?  If so, then I feel like there is an issue with the 'GG or SMS mode' contact pinning in the GearMaster. Not sure of how the code is laid out between the two carts, guessing that the processor is not jumping to the correct init vector in the SMS cart if its in 'GG mode'?!? 

Anyway, it's got to be fairly simple. The GearMaster is just ribbon cable between a SMS cart connector and a GG connector contact board. Either there is a wiring problem or its not making contact somewhere. Just have to sit down with the interconnect drawing and test wink

Last edited by yogi (March 16, 2013 6:41 am)