Recently I was talking to IronGiant about testing the “a78-05-1.52” ROM on an original Bubble Bobble PCB with the Fluke 9010.
As the ROM is banked we cannot test this ROM in one go.
Here is how we managed to do it.
0) Before we do anything we need to disable the watchdog otherwise this wont work properly. This is done by cutting the track on JP6 on the solder side (thanks to IronGiant for the info).
1) Take the ROM dump for “a78-05-1.52” and split it into 4 files using a HEX editor or similar. Each file should be 0x4000 bytes in size.
Run all 4 files through one of the signature calculators that can be found online and make a note of them.
2) The bankswitch lies at address 0xFB40 in the address map.
You need to write a value between 4 and 7 to select the relevant bank.
So start by writing 4 to address 0xFB40.
3) Next we need run a ROM check on between address 0x8000 & 0xBFFF.
This signature should match the first 0x4000 bytes of the ROM.
4) Repeat steps 2 and 3 a further three times incrementing the value written to address 0xFB40 each time. If all the signatures match then the ROM is good.
The ROM is different across each version of this game so make sure you compare it with the right file.
This method will probably work on the bootlegs too with some minor changes to the procedure.