View Full Version : Arcade mod help

10-20-2000, 07:20 PM
I want to switch betwenn old bios and the new Arcade bios.
I got an old mod US/japanese with two bioses switchable in an other Neo. There where only pin 20 cut of the mainbord and liftet off. all other Pins are connected and the japanese bios is on top of the old. On wire goes to a chip on the top left ( was a 3-3 AES mainboard) Can i do it so with the arcademod too ?
In an other Jap/US mod Neo of mine there are the same thing ( pin 20 up ) but there are 2 15K resistors connected to each pin and the other side gos to a chip nearbye ( 3-5 Mainboard ) and the switch choose on of the bioses to the Mainboard.
So what are the resistors for ? extra power supply or to keep the power away ?
In the Arcademod sheet i should do cut of pin 2 and solder the resistor between pin 2 and 40 on the old bios. then i should do a bridge between pin 2 and pin 20 of the new bios. Well this confuses me because the other mods where not like that. Then what is with pin 2 ? Well dont i need to solder it to the mainboard. Well i guess the resitor shut off the power for the old bios and pin 20 powers the new bios . Is that correct ?
Please help and tell me how to switch it in the easyest way.
Huge thanks

10-21-2000, 02:51 PM
Pin 2 is for enabling/disabling a rom.

10-21-2000, 07:35 PM
OK thanks but that dont helped me a lot.
So when i cut pin 2 off the mainboard and dont make any connection how should it then work ? Then i must really know how to switch between the bioses. Whats up with that resistor ??
Thanks for help

10-22-2000, 06:56 AM
When you connect pin 2 directly to pin 20, the bios is ENABLED. When you connect pin 2 to pin 40 via a 15K resistor, the bios is DISABLED.

Hope it'll help you http://www.neo-geo.com/ubb/smile.gif

10-22-2000, 02:03 PM
Tnxs a lot HP Man
That will do it so far i will try it without to connect pin 2 to the mainbord and keep a switch between the bioses.

Well i wonder why the US/Jap mod only cut of the Pin 20.

10-22-2000, 02:27 PM
Well, when pin 20 is lifted from the board, the bios output is disabled...

Quite se same trick as pin 2 (chip enable), using pin 2 is more "elegant" and logical since you disable the whole bios, instead of just disabling the output.

This said, both trick should work equally http://www.neo-geo.com/ubb/wink.gif

10-23-2000, 08:58 AM
Pin 2 is the CE (Chip Enable) line. Basically, clip pin 2 as close to the board as possible from the original bios and pull the leg straight out. Now, on the debug bios, pull up pin 2 so that it's straight out and then place the debug bios directly on top of the old bios. Solder the remaining 39 pins in place (directly over the old bios).

Now, run a 15K resistor to a 5V source (such as pin 40) from each of the #2 pins.

Now, depending on which chip you want to enable, you need to supply G to the CE line. The easiest way -- get at least a SPDT switch. Wire the middle peg of the switch to G (ground). Pin 20 of the BIOS is actually OE (Output Enable), which on the Neo is already set to G. Pin 11 is the actual G line of the BIOS. You can use either of these locations for the G for the switch.

Now, from each of the otter pegs, connect a wire to the #2 pins of the bios'. At this point, you should have 3 wires off the switch. The top wire to one bios (#2 pin), the middle wire to ground (#11 pin?), the bottom wire to the other bios (#2 pin).

Now, when you flip the switch, it will send G to one of the bios chips and the 15K resistor will "pull-up" the 5V to disable the other chip.

Hope the helps explain what is going on and why.


10-23-2000, 06:32 PM
Thanks to booth of u.
Bye the way Jeff, thats almost i planned it to do.
Thanks for the explantation that helped me a lot. Where did u get the info from or the knowlege how the Bios works ?
Some modretrailers here in germany will do the mod for 100$. A little to mutch for me and on the other hand i can do it so too.
How mutch did you paid for the eprom burner ? Here in germany the cheapest is 200 $. I could build a flashrom burner for 50 $ but that thing dont have hold 40 Pins only 32 or 36 or so.
Well i dont have the time to deal with that kind of stuff and i dont have the equipment.
For some friends i do sometimes modjobs but thats all.
I builded some adaptors for PS joypads and 1 memcard reader/writer joyadaptor for PC on LPT .... well those rumble funktion is pretty cool in force feedbackgames http://www.neo-geo.com/ubb/wink.gif . Well i got the instrucktions from the net and some drivers too. Well if someone rewrite the drivers it should be very easy to get an Neo Geo joyboard connected to PC. I saw a mod for the PS very funny to play PS Games with the Neoboard. There where no instruktions so i coulnd make the adaptor... to bad.
Maybee i build the Flashburner next time and burn some Comp bioses or DVD bioses or graficcard bios or............

Thanks a lot !!!!!!!!!!!!!!

10-25-2000, 07:42 PM
Hi the bios works perfect. Great thing.
I had to do it with pin 20 because i had nothing small enoght to cut pin 2.