The Super Game Boy (SGB) was a special cartridge for the Super Nintendo (SNES) that allowed you to play original Game Boy (DMG) games on your Super Nintendo... in living color! Some Game Boy games can even take advantage of enhancements provided by the SGB in ways you wouldn't see on a Game Boy, including custom color palettes, enhanced audio, and screen borders. How does that strike you??
Unfortunately, the original Super Game Boy had one "major" flaw. The clock speed was 2.4% too fast. For most people, this makes no difference, but for true gamers it amounts to blasphemy. The side effect of this is that the Super Game Boy cannot use a link cable to connect with other Game Boys, since the clock speeds would be too dissimilar. Japan got the Super Game Boy 2, which fixed this oversight and added a link port. But everyone else never got it! Thus, true gamers got to work, and created mods that fix the clock speed and add a link port.
Another type of mod that has cropped up over the years are standalone SNES games with a single Game Boy game inside. This generally includes taking the PCB out of a Super Game Boy, taking the PCB out of a Game Boy game (hopefully a reproduction and not an original!), and permanently soldering the Game Boy PCB to the SGB board. A bit rough, but it gets the job done.
The thing about all these different SGB mods is that they consist of boards soldered together to an original SGB board. There hasn't been a single, clean, standalone board that incorporates all these features in a nice, sturdy package. Until now!
This is the Super Game Boy Plus, or SGB+. This circuit board can do the following:
- Allows for three separate clock options:
- the original "wrong" clock speed,
- the correct clock speed, or
- the correct clock speed with the ability to overclock and underclock in-game
- Incorporates the link port onto the board using a small daughter board to offset it into a perfect location on the edge of a standard SNES cartridge (if you are using an SGB2 shell, it will fit without the daughter board)
- Optionally allow you to lock the board to one specific Game Boy game instead of using the cartridge connector - save data can be transplanted to/from the cartridge via the FRAM chip
- Can be used in three different SNES shells with minimal shell trimming required:
- an original Super Game Boy shell with the cartridge connector,
- a standard 46-pin SNES shell (will require two cuts on the bottom of the shell for the extra cart edge pins), and
- a 60-pin SNES shell used for games that used enhancement chips like the SA-1 or SuperFX
There are two versions of the Super Game Boy Plus - one that can be used for standalone MBC3 games (in development), and one that can be used for standalone MBC5 games. If you only want an enhanced Super Game Boy without locking it to a single game, you can use either the MBC3 or MBC5 variant - it does not matter which you pick. Because this project is highly customizable, you must carefully follow the instructions below to help guide you through the assembly process based on your desires.
PLEASE READ THIS GITHUB REPOSITORY IN IT'S ENTIRETY TO ENSURE YOU ASSEMBLE THE CARTRIDGE PROPERLY.
All gerbers and source files can be found in this repo in the two folders linked above, as this project is fully open source.
- This project requires you remove some components from an original Super Game Boy cartridge. This will require a hot air rework station or a hot plate. This will also require extensive soldering capabilities - do not attempt this project if you do not have sufficient soldering experience.
- If you are making a single game without the cartridge connector, you need to have an original Game Boy game that uses an MBC3 or MBC5 mapper chip, so you can remove it and use it on this board. You can find a list of games and their mappers here.
- When soldering parts on, it's a good idea to put kapton tape or otherwise cover the bottom cartridge edge. You do not want to get solder on the cartridge contacts.
- I am not responsible for any damage you do to your self or your property. Attempt this project at your own risk.
- I do not guarantee design compatibility. You may encounter issues with certain games. There is also a chance I have made an error in the design or the BOM - if this is the case, I will do everything I can to address the problem as quickly as possible.
- If you are using this board to make games other than for personal use, you must have permission from the originator to use and distribute any ROM images or other related material. You are responsible for making sure you adhere to any license requirements.
DO NOT use my circuit boards for profiting from stolen work - this especially includes homebrew content, ROM hacks, and using fan-made labels without permission from the originator. Support ALL original creators!
- You will need basic tools, like a soldering iron, hot plate, and/or hot air rework station.
- If you need the cartridge connector for an enhanced SGB build, desoldering needles may be helpful in removing it from the donor board.
- If you're making a single-game SGB+ cartridge, you will need a method of programming the ROM and FRAM (if desired). You cannot program the SGB+ cartridge with a cart programmer, like the OSCR. You need to solder pre-programmed chips.
- In my opinion, the easiest way to do this if you have the equipment already is to make one of my FRAM-enabled Game Boy cartridges, and then transfer the ROM and FRAM chips over to the SGB+ board. You can use a variety of cart flashers, such as GBxCart and the OSCR to load the game and save data onto the catridge. Doing it this way, you can also test the game in a Game Boy before you move the chips over to make sure it's in working order. As a bonus, all of the parts on the FRAM board are named the same as on the SGB+ board, making part transferrals even easier to manage.
- Alternatively, the T48 programmer with the TSOP48 adapter can program the ROM chip.
- If you want to add clock control options (overclocking/underclocking), you will need a way of programming an ATTINY85. My preferred method is to use an Arduino Uno or Arduino Mega, as I own those already. The instructions I provide will be using an Arduino to program the ATTINY. There are a multitude of other ways as well, but you will need to figure those out for yourself.
- You may need to do some shell cuts to get things to fit, like the link port. I recommend using a file set - I bought this one.
These are listed in the BOMs in the MBC3 and MBC5 folders, but for quick reference, you will need:
- Super Game Boy CPU
- ICD2 Interface chip
- SNES Mask ROM (bottom right chip)
These parts are salvagable from the SGB (recommended), but there are alternate options listed in the BOM:
- 2x SRAM
- CIC Region Lockout (the 18-pin device in the middle)
To start off, here is a bird's-eye view of the process to populate one of these boards. Please follow this flowchart as you go. I highly recommend testing the board in a SNES after you solder the Group A components. This will help narrow down issues early on, before you start messing with things like overclocking.
First, populate the entire board with the Group A components. That's the majority of them. Also, solder the CLK1 solder pads on the back of the board to enable the SNES-driven clock just for testing. When you pop it into the SNES (obviously without a Game Boy game), you should see this screen:
If you've got that, then you know you at least got the essentials soldered properly. If you get the Game Boy border, but no cartridge error, then you have some kind of problem somewhere on the GB-side (like the SGB CPU, the ICD2, the RAM chips, etc). If you just get a fully black screen, then either the cartridge might not be making good contact with the SNES cartridge connector (or the cart connector is dirty), or you have some issue with the SNES-side components like the mask ROM or the CIC (if you're using the PIC12F629, make sure the SuperCIC code is programmed properly). You may also have a solder bridge anywhere on the board.
If you're not planning on fixing the clock speed, and keeping it at the incorrect 4.295 MHz frequency, then you don't have to do anything else for this step. Skip ahead to Step 3! Otherwise, read on.
Note that for all of these clock options, you can populate Group B and C components at the same time without causing any issues. The CLK pads on the back of the board will dictate which of these components have control over the clock generation, and they can't interfere with each other (as long as you only bridge one set of CLK pads).
This is the simplest clock modification, all you have to do is solder the few Group B components, desolder CLK1, and solder bridge CLK2. This will yield the proper clock speed of 4.194 MHz.
This one will take some work, because you will need to program the ATTINY85. You will need to program it with my custom-developed code. You can do this before soldering, or after soldering if you use the ISP header pins. In either case, populate Group C components, desolder CLK1, and solder bridge CLK3 to set up the board for the clock generator.
I will briefly walk through how to program the ATTINY85 after it is soldered to the board, through the ISP header pins, with an Arduino Mega, but you should closely follow the guides I link. If you ask me how to program the chip, or why it isn't programming properly, my answer is going to be "read the tutorial." If you are using a different method of programming, you will have to find instructions yourself.
Here is detailed instructions for using an Arduino Uno to program an ATTINY85. I haven't used them myself, but they look to be correct. I personally use a Mega to program my ATTINY chips; the detailed instructions can be found here for the Arduino Mega. Again, it is crucial you follow these instructions closely to get it working.
One thing I have done differently than these tutorials in the first steps is the choice of ATTINY core, which you need to communicate with the ATTINY through the Arduino IDE. I use ATTinyCore by SpenceKonde, which you can find here. I recommend using this one instead.
Anyway, here's a general guideline for programming the chip:
- Program the host Arduino to be an ISP programmer. If using the Mega, follow the instructions in the link above to change the pin definitions in the ArduinoISP code to match the Mega instead of the Uno.
- Put SW1 in PROG mode to allow programming of the ATTINY85.
- Connect the Arduino pins to the ISP header as such:
- Connect ISP pin 1 (PB1, PICO on the ATTINY85) to Arduino PICO pin (50 on Mega, 12 on Uno)
- Connect ISP pin 2 (5V) to the Arduino 5V pin
- Connect ISP pin 3 (PB2, SCK on the ATTINY85) to Arduino SCK pin (52 on Mega, 13 on Uno)
- Connect ISP pin 4 (PB0, POCI on the ATTINY85) to Arduino POCI pin (51 on Mega, 11 on Uno)
- Connect ISP pin 5 (RST, SS on the ATTINY85) to Arduino SS pin (53 on Mega, 10 on Uno)
- Connect ISP pin 6 (GND) to the Arduino GND pin
- Burn the bootloader to the ATTINY85 (Tools > Burn Bootloader). Make sure the processor is set to run on the internal 8 MHz clock, not an external clock. Not burning the bootloader is a common cause of failure when people are trying to program these chips.
- Upload the Arduino sketch provided above onto the ATTINY85. When programming the ATTINY, my drop down menu looks like this:
- If it uploads correctly, unplug all the wires and switch SW1 to PLAY mode. It will not work if it remains in PROG mode.
Remember, if you put the cartridge in your SNES and get a Game Boy border but no blinking cartridge error then that means there's an issue with the clock. You will know you did it right if you get the blinking error screen posted above.
If you don't want to deal with an ATTINY85, the board is fully compatible with qwertymodo's SGB clock mod. The downside to this is that if you want to change the clock speed, you will still need to buy the Super Game Boy Commander controller from Hori... and those are not cheap. The main draw to qwertymodo's mod under normal circumstances is the clock speed is fixed, however since you can fix it pretty easily by soldering in the Group B components, the usefulness is a bit diminished. But in any case, it is still an option. All you have to do is follow the instructions on his site to install it, they apply to my SGB+ boards as well. Make sure the CLK1 pads remain bridged.
Please note that if you want to add the link port, you must be using one of the clock options that fix the frequency (this also includes the overclocking option with the ATTINY85, as that defaults to 4.194 MHz). The link port will not work if your clock speed is the incorrect 4.295 MHz provided by the SNES.
Firstly, if for some reason you have a junked Japanese-only SGB2 cartridge with an in-tact shell (the blue one that has a cutout for the link port) then you only need to add the link port in the P1 socket. Again, though, the SGB2 is not compatible with this mod, so don't buy one as a donor, because you can't use it for parts.
Image from gekkio's Game Boy Hardware Database.
If you are NOT using an SGB2 shell, which I would guess you are not then you'll need to offset the link port from the board vertically to get it to fit in the shell nicely. You will also need to cut out a hole in the SNES shell, obviously.
Getting the link port adapter board to sit level is a bit tricky. You also need to make sure the board is placed in the correct way, and not flipped around. The way I do it is:
- Solder the 2x3 headers (these have 2mm spacing instead of the standard 2.54mm spacing) into the link port adapter board. Make sure the headers are soldered onto the adapter board in such a way that it would be sandwiched between the main PCB and the adapter PCB.
- Solder the 1x2 header (these have the standard 2.54mm spacing) onto the SGB+ board. You will also need to remove the black housing, as that is thicker than the housing on the 2x3 header (which is 1.5mm), so the board would be crooked if this was kept in. Use flush cutters or some other tool to carefully remove them without bending the pins.
-
Optional - place the 3D printed spacer I have linked above on top of the SGB+ board to help level the adapter board. If you don't have a 3D printer, you can use another link adapter board as a temporary shim (if you get them in the 1.6mm thickness) to achieve approximately the same effect.
-
With the adapter board placed on the main SGB+ board, finish soldering the eight pins - I like to solder the two structural headers, then flip the board over and do the remaining six pins going into the P1 socket on the SGB+ board. Trim down the structural header pins after you're done.
- Finally, solder the link port onto the adapter board, making sure it's also placed in the right direction on the correct side of the board.
This is how it should look from the "topside" of the board. (Note that this picture does not include the 3D printed spacer.)
I detail shell trimming farther down.
If you're planning on retaining the cartridge connector in your build, then solder in the cartridge connector now! I recommend taking the time to clean it out with some isopropyl alcohol to get better contact with Game Boy carts, since you've got it outside the shell anyway. Then, you're done! (This is the only Group E component)
If you're planning on locking the cartridge to a single game, then you have some more work to do. You need to program the M29F160 chip with the ROM of the game you want to make. You can do this in one of two ways:
- With a standalone programmer like the T48 programmer with the TSOP48 adapter - just place the chip in the adapter, load the ROM file in the programming software, and flash the chip
OR
- Build a Game Boy cartridge that uses the M29F160 (like my FRAM MBC3 boards, or FRAM MBC5 boards), flash the game using a cart flasher like the GBxCart or the OSCR, then desolder the chips and move them over to the SGB+ board. Note that for my FRAM boards, I use the same reference designators on the Game Boy boards as I do on these SGB+ boards, making matching up the parts a lot easier if you're transferring them over. (Note: the following picture is an old design where the reference designators are different. Ignore it!)
The upside to #2 is that you can test the game out in an actual Game Boy before transferring the chips over, and you can flash save data onto the FRAM if you have a game already started on a different cartridge you've dumped. So personally, I use method #2 if I can.
After you've programmed your ROM (and optionally FRAM) chip(s), then solder them to the board, along with the rest of the Group F components.
Note: The board will not fit in a Super Game Boy shell if you have soldered in the Group F components.
At this point - you've completed assembly of the cartridge electronics! Test it in a SNES to make sure it works properly.
As mentioned, other than the SGB2 shell, there are three different shells this circuit board is compatible with: an original Super Game Boy shell with the cartridge connector, a standard 46-pin SNES shell, and a 60-pin SNES shell used for games that used enhancement chips like the SA-1 or SuperFX. This section will go over the (potential) shell cuts you may need for your build, depending on what features you're including and which shell you're using. (Spoiler alert: the 60-pin shells require the fewest amount of cuts.)
Along with the trimming below for the link port, you will need to do a few minor trims on the SGB shell if you're making an enhanced SGB cartridge, that I recommend tackling first before you move onto the big trim.
There's this ridge here near where the link port will be going on the back shell. This doesn't need to be an extremely clean cut.
On the front shell, you will also need to trim off this post, as it interferes with the link port board.
Now to cover the actual trimming required for letting the link port stick out, which will be applicable to all the shell types.
If you are adding a link port, and you aren't using an SGB2 shell, you will need to do a cut on every shell to accomodate the link port. I've created a 3D model you can 3D print in order to help line up the cut you need to make; it is also linked at the top of this repository. The print sits on top of the shell and has a cutout where you can start your cut for the link port. Note that this is only a starting point. You will need to shave back the shell more to get it to fit - go slowly, be patient, or you will get ugly cuts. Cut the area highlighted in yellow below.
You should also do a cut on the top half of the shell, where the link port will sit, to make sure it closes nicely. I don't have a guide made up for this one, since it's a pretty minor cut. Just line it up, and shave off the section.
Standard SNES shells only have one cut on the bottom of the shell to allow the middle 46 cart edge pins to stick through. But the Super Game Boy uses the extra 16 expansion pins on either end. So you'll have to cut two slots for those parts of the cart edge to stick through. The easiest way I've been able to do this is to line up the middle 46 pins, and sit the board a bit above that so you can see the plastic you'll need to cut. Then, mark the area you'll have to cut with a marker, and go over it with a file. I highly recommend against using flush cutters to make a starting cut, because the plastic will snap off really easily all the way towards the middle, and you'll be missing the two little nubs.
Since this is still a Super Game Boy... probably just good to look at the Super Game Boy manual for all the controls that go with that.
Other than that - if you've installed the clock mod onto your board, this is how you control it if you use the code I provide. You only need to use the Start and Select buttons to change speeds. In the code, I have allocated space for seven different clock settings, and it starts at 1x by default (the correct 4.194 MHz clock speed). Note that each clock speed will affect the audio as well - it is not like Dodrio mode in Pokemon Stadium's GB Tower where the audio is unaffected. This means playing games can get... annoying at really high clock speeds.
The default clock multiplier settings are in order: 0.5x, 0.67x, 0.8x, 1x, 1.25x, 1.5x, 2x. A clock multiplier of 3x works, but produces a lot of graphical glitches. 4x and higher becomes unstable and will freeze the game.
- Speeding up: Press and hold Select first, wait a second, then also press and hold Start simultaneously (imitating a "fast forward" button)
- Slowing down: Press and hold Start first, wait a second, then also press and hold Select simultaneously (imitating a "rewind" button)
- Continuing to hold these two buttons down will continue up/down the list of clock multipliers in the code until it hits the maximum/minimum, with approximately a 2 second delay between switching
If you want, you can also disable the clock change function, allowing you to use the Start and Select buttons freely (though, I can't think of any game that requires you press these buttons simultaneously for longer than a few seconds). To do this:
- Press and hold both Start and Select at the same time and hold down for approximately 5 seconds.
- If your clock speed is something other than the 1x setting, it will be reset back to 1x.
- At this point, you have disabled the clock change function: pressing Start/Select will no longer change the clock speed.
- To re-enable clock control, press and hold Start and Select at the same time and hold down for approximately 5 seconds.
Power cycling the SNES will also re-enable the clock control function.
Q: Will these boards fit in Super Famicom shells?
A: I am pretty sure they do, but I don't have any to try out. If you're able to confirm they fit for me, please let me know, and I will update this question accordingly.
Q: Does this work with a DMG CPU instead of a SGB CPU?
A: Unfortunately, no, but it would be really nice if you could.
Q: Does this work with a SGB2 CPU instead of a SGB CPU?
A: No, please do not destroy a SGB2 for this project!
Q: Can you make one for me?
A: No.
Q: But what if I pay you?
A: NO.
Q: Can I make Game Boy Color games with this?
A: No.
Q: Can you make a board that lets you play Game Boy Color games on the SNES?
A: Not without FPGA wizardry, which is something I don't want to deal with.
- Enormous thanks to Gekkio for their Super Game Boy reverse engineering work. This repository was the basis of this project, and he saved me hours and hours of time. He is the hero we don't deserve.
- Qwertymodo's work with the clock mod and link port additions really helped me out in designing my own. Huge thanks for his findings, and all he has contributed to the gaming space!
- Thanks to Adafruit for providing the basis of the clock generator circuit.
- Special thanks to beta tester olDirdey from discord, for providing some feedback on the link port and suggesting the 2-pin structural support header.
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. You are able to copy and redistribute the material in any medium or format, as well as remix, transform, or build upon the material for any purpose (even commercial) - but you must give appropriate credit, provide a link to the license, and indicate if any changes were made.
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