Permanent Cart Slot Fix - Hard-Wiring

Continuing this from the Psuedo Saturn Kai thread, so as to not hijack that thread. The ultimate goal of this project is to:

1) Delete the failed cart connector
2) Hard-wire a AR 4M Plus cart to Saturn motherboard
3) Flash AR cart with Pseudo Saturn Kai, for ultimate saturn gaming functionality and permanent failed cart connector fix
4) Implement manual cart enable/disable functionality
5) Conceal mod within case (with possible exception of a on/off switch for cart enable/disable)
Item #3 requires successful achievement of #4.

All 5V lines desoldered from hard-wired cart (8 total), resulting in Saturn booting normally (not into Action Replay operation), but with extended memory (1MB/4M). I also determined in the process that the hard-wired AR cart would continue to boot and apparently function normally with only 2 5V lines connected. However, I am unsure of the power draw of the cart. The 26 ga wire used for the hard-wiring is good for up to 1.3A per wire, and not a likely failure point. Motherboard traces could possibly overheat and fail if all 8 5V connections are not connected at the cart. Switching all 8 lines, even through a single switch, is not desirable for mutliple reasons - space constraints, extra solder joint failure points.

Member cafe-alpha suggested that pin A47 (A-bus CS0) could potentially function to enable/disable the cart through a simple on/off switch. I desoldered pin A47 and it had no apparent effect. The cart continued to apparently operate normally, botting X-men vs. SF on a US Saturn and playing normally. Referencing the below pinout and , pin A47 corresponds to PAL22V10 pin 2, which is input1.

So, I'm continuing to look for a single line that will offer enable/disable functionality if switched by a simple on/off switch.

Manual also referenced, which I see calls out pin A47 as A-bus CS0, but I also notice that it is for PAL Saturns. Not sure if that makes any difference for my US Saturn efforts:,_June,_1995.pdf
Found the equivalent pin on NTSC Saturn - it's pin A45. Desoldered it, and the cart is disabled. :D

It's not A45 (Address Bus bit 0) on your schematic ... but should do the job anyway since Saturn won't boot if it doesn't sees "SEGA SEGASATURN " string at the beginning of cartridge flash ROM :) Basically, disconnecting pins related to data and/or address buses makes cartridge not booting, but that's not a clean (long term) way to do.

Please find below location of CS0 pin :
On cartridge rear side, from middle to left side of Saturn connector : 4 pins from address bus -> GND pin -> 4 other pins from address bus -> GND -> CS0.

If you want to add a cartridge enable/disable switch, please connect it as follow :
- Middle pin : CS0 on cartridge side
- Left pin : CS0 on Saturn side
- Right pin : VCC, on Saturn side or cartridge side as you want
For example, pins at cartridge's rear side, both extremities are VCC.

Disclaimer : this is *NOT* tested, please do at your own risks ! No warranty it will work, no responsibility, etc.

Edit : as indicated in a previous post from me, a simple open/close switch won't do the job : CS0 needs to be connected to either Saturn (in order to enable cartridge) or VCC (to disable the cartridge, because CS0 is active at low state). Disconnecting it will lead to undefined behavior.
Last edited:
Well, putting a simple "break" switch on pin A45 seems to have done the trick. Setting the switch to "off" disables the cart and the Saturn operates as if no cart is inserted. Setting the switch to "on", the Saturn operates with full cart functionality. Nonetheless, I linked your post in the description of my youtube video, as being a possibly better way to achieve the enable/disable function. I trust you are right, but can't fully endorse it unless I've tested it personally, and at this point I have no intentions of re-opening my Saturn for a long while. So, sorry for the legalese of using the word "possibly".

At any rate, the mod is completed, and Pseudo Saturn Kai Lite has been flashed to the hard-wired cart.

Last edited:
Great ! I'm relieved your mod completed successfully !!
Goal was to get Pseudo Saturn Kai working on your Saturn, and not verifying if pin X or pin Y is better, so of course there's no need to verify if my suggestion works or not :)
Great ! I'm relieved your mod completed successfully !!
You and me both. This effort took almost a full week, starting on a Sunday and consuming nearly every waking minute after work (often staying up much later than I should have). :hungover: Hopefully it is useful for others. While the Rhea/Phoebe solution is pretty awesome, and the currently available modchip is a great all-in-one solution for modding any version of the Saturn, do either of them solve for the issue of not having 1MB/4MB memory extension when the cart slot fails? Maybe this effort was unnecessary if they do, but I also like the fact of running in as much of a native state as possible - games running from CD, 1MB/4MB memory extension present when needed, and no outwardly visible signs of modification - a sleeper, if you will. :)

To that end, I've been putting the system through its paces today:
Mod toggled on: D&D Shadows Over Mystara backup, Marverl Super Heroes vs. Street Fighter, Formula Karts backup
Mod toggled off: Street Fighter Alpha 2, Street Fighter Collectoin - Super Street Fighter 2 (managed to achieve 1.5M+ 1cc on max difficulty :cool: )

All working flawlessly. :D
Last edited:
You're quite fast : I personally couldn't have finished such kind of project in a single week !
Rhea/Phoebe and Action Replay with Pseudo Saturn Kai are two distinct mods : for example, Rhea/Phoebe only won't be any help for games requiring RAM cartridges. On the other side, using an ODE is convenient if you want to test many different games.
I like keeping hardware as much of a native state as possible too, so please enjoy the sound of your Saturn CD drive seeking or spinning while playing :)

(PS : Pseudo Saturn Kai unlocks CD-ROM unit only if required, so there's no need to turn off the mod when playing original games)
Here's a line diagram, including only the necessary connections/contacts that need to be wired, the AR contact numbering scheme used at the refence link, and the motherboard solder joint numbering scheme printed on the board (also corroborated with the schematic posted above). Hopefully this is helpful, if anyone else wants to do this mod.


  • Saturn CartConnector-AR Line Diagram.pdf
    22.3 KB · Views: 321