Sega Saturn Save Memory

Discussion in 'Modding and Hacking - Consoles and Electronics' started by Korn16ftl3, Oct 8, 2017.

  1. Korn16ftl3

    Korn16ftl3 Spirited Member

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    So I had a Google around and stumbled across an fram mod for the sega saturn...that's pretty neat and would save a lot of people there hard work from being lost when the battery dies as it does not need the battery at all. We also have other mods like the region free BIOS because the modchip does not circumvent the region lock. We also can control the refresh rate with a 50/60hz mod. The last issue I can see needing a resolution would be the small amount of space we have available for storage on our systems. I was curious how hard it would be for an upgrade for the internal memory storage for game saves? I'm aware that the amount usable is determined by the BIOS (or at least from reading) but has anyone attempted this or know more about this as a possibility even?

    I found this while reading around about the FRAM mod:
    http://segasaturngroup.proboards.com/thread/8731/saturn-internal-sram-mods

    Even using a page system like he had sorted out would be great.
    I'm just thinking that the less we have to rely on the cartridge slot the better off we are as they are known for having issues.

    If the save space could somehow be expanded or at least more available to select (like the above thread apparently accomplished?) Then the only real need for the cartridge slot would be a 1M or 4M ram cart and even if the cartridge slot was to completely die we would be able to permanently attach a ram cart
     
  2. WingMantis

    WingMantis Active Member

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    I was actually searching for info about an FRAM mod for the Saturn today too. I stumbled on the same forum in your link. The guy didn't mention too many details about FRAM. He did talk about a Region Free Bios making it possible to hook up 2 more address lines so you could get 4x the on-board save memory. I'll search the forum here, but where is this bios mod info? Can you link it?

    How hard is resetting on the system? I assume it's not as bad as a full on power off and power on? That's how he's switching banks. I don't like all the wires everywhere though. 1024Kb or 2048 of FRAM in one bank would be amazing if there is someway to hook up 4 more address lines.


    I also found this link though from someone that did a 1:1 save memory FRAM replacement https://db-electronics.ca/2017/02/10/sega-saturn-internal-memory-mod-with-fram-no-battery-required/
     
  3. Korn16ftl3

    Korn16ftl3 Spirited Member

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    I didn't find any further details on my links mod nor any downloads or schematics. I'm assuming he added the lines to the original region free bios mod. He did say he tried contacting the author because he wanted to simply enable the full size of the fram via rewriting the bios which is where the fram limitation exists from my understanding
     
  4. Korn16ftl3

    Korn16ftl3 Spirited Member

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    It seems we need someone who knows how to reverse and modify the sega saturn bios to simply be able to swap chips and have write access to the entire chip
     
  5. WingMantis

    WingMantis Active Member

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    The link I posted has a couple part numbers for the stock SRAM, and the FRAM that guy used and he has some schematics. The guy there just replaced with the same size FRAM so he doesn't have to worry about battery going bad and losing saves. In fact he didn't put a battery back in for the real time clock. You would probably have to cut a trace or something to isolate the FRAM from the battery power. The yellow wire is the only actual mod he did to the new ram chip. That pin is the activator for save ram access, and the new chip was opposite polarity for signaling (high instead of low or vice versa). The other shunts he added are because he damaged the surface mount pads for a few pins and he had to tie into the trace further along.

    I think I understand what the guy did on the link you posted too. I tried looking for some bigger ram chips, and it seems that the stock chip is parallel addressing. Anything larger than this size (with the same 28 pin footprint) goes to a serial-parallel hybrid setup. It's kind of like the front and rear gears on a multi-speed bicycle

    He set up the PIC controller to switch the active access lines between 4 different blocks of a single 1024kbits. I think If he had been able to get the BIOS mod, the system would control the extra access lines and be able to see the whole thing at once without the PIC or extra wiring.

    We just have to find out about this BIOS mod. Where it is, is it open source or cheap enough to pay for, etc.
     
  6. Bad_Ad84

    Bad_Ad84 Keyboard Error: Press F1 to Continue

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    There is no bios mod that allows access to the full extra space. You need to manually change banks.

    Or someone could try making the bios, but currently it doesn't exist.
     
  7. Korn16ftl3

    Korn16ftl3 Spirited Member

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    That's what I thought as the op in my link could not get ahold of the author of the region free bios to see about implementing these changes
     
  8. Korn16ftl3

    Korn16ftl3 Spirited Member

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    Is or would there be a way to power let's say 2 chips and select which one was powered on somehow with something like a switchless mod or small 3 way tactile switch?

    I'm thinking perhaps the FRAM mod with a second FRAM chip piggy backed on top jist like the Dreamcast bios mod or something to that effect.
     
  9. Bad_Ad84

    Bad_Ad84 Keyboard Error: Press F1 to Continue

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    that is more work that just using a larger chip.

    If you install a chip that is 2x the size of the original, you just have a switch on the last address line and change it between high and low (1,0 or +5v and ground)
     
  10. Korn16ftl3

    Korn16ftl3 Spirited Member

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    See I have no knowledge of anything like that but it sounds like it makes mich more sense....is that what the poster of the thread I linked did I'm guessing?
     
  11. Korn16ftl3

    Korn16ftl3 Spirited Member

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  12. Korn16ftl3

    Korn16ftl3 Spirited Member

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    So apparently or from reading anyways it is assumed here:

    https://assemblergames.com/threads/sega-saturn-region-free-bios.33602/page-3

    That IDA pro was used to disassemble the saturn BIOS
    Now I'm curious about how to add larger memory support to the original BIOS.
    Perhaps I will track down a copy of this program and take a look just for fun as I'm curious about what a BIOS actually looks like also
     
  13. Bad_Ad84

    Bad_Ad84 Keyboard Error: Press F1 to Continue

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    It's no simple task. You will need to know superH assembly.
     
  14. Korn16ftl3

    Korn16ftl3 Spirited Member

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    Ya ok...already beyond my knowledge lol
     
  15. WingMantis

    WingMantis Active Member

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    Hi @Bad_Ad84 thanks for dropping in and for the feedback. I posted a link to this thread in one of the Bios mod threads to see if we can get more people here. Or is there a thread about this already? I didn't see anything, and a lot of assembler links are dead ends...The linked project looks pretty sloppy and he doesn't have schematics or pic program link.

    @Korn16ftl3 The guy that upgraded his capacity basically used the switchless region method to switch between banks. So going that route would interfere if you wanted to use the reset button for region switching.
     
  16. Korn16ftl3

    Korn16ftl3 Spirited Member

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    Different thought same sort of concept behind it....what about the arp cartridges? I know with a mod like pseudo saturn u can't have the save feature......are the chips in the arp swappable with something 2x larger that we can switch between? That would give is both save feature and the backup feature all with a switch of some sort
     
  17. A Murder of Crows

    A Murder of Crows Spirited Member

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    The save feature is re-instated on Cafe-Alpha's "Saturn Gamer's Cart". You lose the 4MB Expansion RAM for Capcom fighters and the like, but you gain save data directly to the cart for games that support that (PDS won't work as the JHL launch would have to be run to launch the game, but that launch method doesn't support external devices on the cart if used). He's also added cheat codes in a recent update.

    the Pseudo Saturn Kai Lite works on the ARP. In theory, if you could alter the chips on an ARP and could get full Kai running on it, you might see some interesting and unexpected reactions from the cart.
     
  18. Korn16ftl3

    Korn16ftl3 Spirited Member

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    This whole thought was just a proposal/thought that randomly came to mind being that we are discussing the save memory of the saturn into this topic. I don't believe I have the skills or know how to start such a project just thought it was an interesting concept/thought to bring to the table while we were on this topic
     
  19. Korn16ftl3

    Korn16ftl3 Spirited Member

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    After a bit of reading (some from the original link about the region free bios I posted) the sega saturn uses an sh-2 processor (supported by IDA) but so is the CPS3 (sega related?) So I began to Google about for and sh-2 bios and came up with several for the CPS3 ( http://64darksoft.blogspot.com/2013/08/one-bios-to-rule-them-all-and-one-cdto.html?m=1 ) my question is how are they modifying the BIOS and their methods of modifying and reversing the CPS3 bios be of use to anyone wanting to do the same to the sega saturn BIOS as its the same processor and I would assume reads the same kind of BIOS just with a different instruction set?
     
    Last edited: Oct 10, 2017
  20. Korn16ftl3

    Korn16ftl3 Spirited Member

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    Last edited: Oct 11, 2017

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