Hey everyone I designed a board to handel the reset button for ROM bank select.  The way this works is you program 2 ROMs to a chip, say Goddess of Wisdom and Parallel Worlds.  You disconnect the highest address line from the PCB and connect it to pad A# then connect the VCC, Reset and GND lines then you can select between the 2 games by hitting the reset button on the SNES.

(Install larger RAM chip and connect the highest SRAM address line to A# also to have saves for both games)

I have not printed this board yet but I made a prototype on a bread board with through hole parts and it worked so it should be good.
I will probably have some printed next month as I just started a new job and want to wait for my first check to come in.

Here is the schematic, it was given to me by markfrizbie


And my design in Free PCB


The 393 is a SOP-14 part

Caps and resistor are SMD 0805

Dual diode is SOT23

Output Q0 just switches between 0 and 1, so the other outputs are useless, right? Have you considered using s shift register to design a bank switcher with 4+ banks instead of just 2? I think I did that once, but I have since lost it.

For everyone's information, a BAT54C will work for the diode.

You could connect the highest address line to Q1 and the second highest to Q0 that would give you a 4 bank select according to the counting table, I only wanted to switch between the upper and lower half of the chip so I am only using Q0

BTW forgot to mention I did not design the schematic only the PCB

Is there anything like this for NES?

Looks like the CIC connects to the reset line on NES so this should work as long as you use 2 ROMs that are compatible with the PCB that you are using.

Will need to upgrade your SRAM on the board also.

Say you want to put Sweet Home and Final Fantasy 2 on the same cart they are both SNROM. You would need to pad your ROMs to both be the same size then pick a chip that will hold both of the games.

Upgrade the SRAM and leave the highest address line floating, then rewire the EEPROM to the board but again leave the highest address line floating.

Then wire up this PCB to the highest address line on the SRAM and EEPROM then hitting Reset should switch between the 2 games.

Updated my board design

/bookmarked 'cuz Awesome

MrPete1985 ++

Just noticed that I need to fix the new PCB don't go having the boards printed just yet

EDIT: OK it's fixed

Pete, This is an excellent approach towards increasing the storage space and it's commonly utilized by all major manufacturers of External RAM. The highest address bit can serve as a chip/bank select between different storage. However, it has been correctly pointed out that since only Q0 is being under-utilized. Is there any specific reason for using the HC393 here?

pcb assembly parts

Because that's what the person that gave me the schematic said to use...

You could also connect the an address line to Q1 like I said before but I only needed to switch between 2 games so that's why I did not make a via for it.

Can this be made to work between an original ROM and an EPROM? IOW, can I make a repro out of another game and switch between the original game and the repro game without dumping the original and putting it on the same chip as the repro ROM?

Even if I can't, this is still awesome. I can put the English and Japanese game on the same game pak!

If they both fit on a single chip and are the same size you could, you would probable have to upgrade the SRAM, I think most of the translations cannot load an original SFC save file.

If you wanted to use multiple chips and switch between the 2 chips you would have to add an inverter connect the /CE lines to the board

For multiple chips, size doesn't matter...

Another concern: Reset doesn't initialize the system memory. It's why games like Mario Kart remember your previous character and difficulty selections and Ken Griffey's Winning Run Baseball lets you skip the intro (makes sense to press reset as soon as you power that one on!). Does this initialize the console's memory when you reset?

No it doesn't.

When I was testing the ancient stone tablets on real hardware I saw that some bugs (that always were there in the first run of game) were dissapearing when I was in my second run of the game...

The reset line only restarts the ppu, and not sure but the cic check too.