Neo Geo Switchable Multi Bios

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    • Neo Geo Switchable Multi Bios

      While testing around with the Multi MVS I found myself wishing for an easy way to use different MVS Bioses. Unibios is nice, but its just not original, vanilla, official whatever. Jap v3 is cool but not understanding what is said in most of the games sucks.
      So I started looking around and was a bit puzzled that nobody made something like that. (Well there was one build but I dont want a "hunchback" addon and I want more than 2 bios options)

      Some people mentiond a bankswitching option but there is no tutotial anywhere how to get this done (at least I couldnt find one).

      Now here the solution I came up with:

      The Why:

      - 4 different Bioses selectable gives nice options.
      - No need to modify anything on the MVS/AES board itself. So its completely and tracelessly removable.
      - Its easy to build. "My first mod" kind of easy.
      - Its quick to make. Like 30 minutes.
      - Its cheap. All the parts cost me like $5 on Aliexpress

      The How

      It uses a 27c4096 eprom. Thats 4 times the size of the normal bios eprom. And using simple bank switching you can select one of the 4 different banks.

      The Parts

      1x 27C4096 (I used an AM27C4096-95DC)
      2x Miniature Toggle switch (3 pin - On-On)
      2x 40pin DIP socket. (Best use the cheap ones with easyly bendable legs)
      a piece of wire. (best cut up an old USB cable)

      (See pic1)

      The Tools

      Soldering Station and the usual soldering equipment (tin, flux, pliers....)
      Eprom Programmer (Yes. You need one or at least access to one. If you want to bite the bullet: Aliexpress sells pretty decent ones for like $50)

      Preparing the bios file

      Copy the 4 bios files you want to use in an empty directory. I used Jap v3 (jap3.bin), Euro v2 (EU2.BIN), US v2 (us2.bin) and Unibios 3.3 (uni33.bin).
      Open a DOS shell and go to this directory.
      Enter: "copy/b jap3.bin+eu2.bin+us2.bin+uni33.bin 4k.bin"
      (if you used the same filenames as I did)
      Now burn the 4k.bin file onto your 27c4096 eprom.


      Take one of the sockets and bend pin 38 and pin 39 outward at a right angle (all the way).
      (Google Dip chip numbering if you are unsure. ALWAYS make sure you know where the nook is in the chip and in the sockets so you dont accidentally put things together the wrong way.)

      Now solder one wire to pin 30, one to pin 38, one to pin 39 and one to pin 40. Make sure you solder the one to 30 and 40 in a way that leves the pins themselves free to connect to the second socket.
      Now connect the other end of the wire from pin 30 to the top pin of BOTH switches. Connect the one from pin 40 to the bottom pin of both switches. And finally connect the one from 38 to ONE of the middle pins and 39 to the other switch's middle pin.

      It should now look something like pic 2

      Take the second socket and press your soldered one into it. Be careful not to bend pins. Check if all the pins have connection through both sockets except pin 38 and 39 which MUST NOT have connection. When in doubt use a Multimeter and do a continuity test. You might clip pin 38 and 39 of the second socket to be sure there is no connection to the board later on.

      Then press the programmed eprom into the socket. Again check for alignment of the nook and take care not to bend pins.

      It should now look like pic 3.

      Now take out your bios chip in your Neo Geo and plug in the construct we made. Be careful. Use a chip puller or a flat plastic lever not to damage the board. And again check for the nook to get alignment right.
      Find a nice place for the two switches.

      It should look like pic 4 :D (kinda)

      You are done. The 2 switches have 4 possible combinations each corresponding to one bios you programmed.

      Have Fun!
      And if you find errors or mistakes let me know. I use this for some time now and it works very well.
      Like I said its pretty basic but maybe it gives some of you an idea. Or a newbie to the hobby a nice first project.
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      "No hidden button combos"

      The post was edited 1 time, last by DenTarr ().