PCM chip on bootleg Puzzle Bobble

[adgenet]

My mvs came with a bootleg (surprising nobody) puzzle bobble. My only mvs cart at the moment, and enjoying it very much, but I am looking forward to picking up some legitimate games of course...How much is a Money Idol Exchanger cart?

Anyway, I opened it up to put stickers on the undoubtedly uncovered eproms, and clean the board up a bit and found that the PCM chip had the leg of pin 76 apparently intentionally broken off, and pin 75 of the chip connected to the pads of both 75 and 76 with a blob of solder:


From the dev wiki, these are apparently VA18 and VA19. I saw on mvs-scans that PROG 4096 and the CHA 42-G this bootleg uses are not the boards normally used for puzzle bobble (PROGTOP and CHA256).
Pic of my prog board:


Does this simply have to do with how they basically put the game on a different prog board with eproms?
I tried removing the solder blob and got some minor glitchy audio on the title screen so i put it back, which restored proper audio.
The game runs perfectly, through all levels, as well as 2-player, and I can't spot any glitchiness whatsoever but was curious if anybody has any idea what the clearly intentional clipping of the leg and the solder bridge is about. I couldn't find any other examples of this configuration bootleg anywhere.

I know it really doesn't matter at all since it works fine, and is a bootleg anyway, but I am always looking to learn about the how and why of things if I can.

 

[Supergun]

I can’t tell you the “how” when it comes to doing those things to manipulate different boards to run different games, but I can tell you the “why”; as I have seen mods like that, dozens of times on bootleg carts.

The main thing to remember is: not all bootlegs are created equal. This is done by the cheapest of pirates to save money. In order to be “economically viable” to assemble and sell bootleg carts, you have to keep costs at an absolute minimum. And so you want to be able to use common carts as your donors. But of course, not all carts are compatible with every game. Their are size restrictions and sound changes and copy protections and all other kinds of things that SNK implemented from 1990 to 2004 during the natural lifespan of the neogeo.

So while some bootleg carts can be repurposed, recycled, or reversed, others have been “permanently modified” to a point where they will pretty much never serve another purpose, other then what they were changed to. So for example, in your case, the cart works fine as a bust a move / puzzle bobble, so then just leave it as such. No sense losing sleep over it. You weren’t the one who ruined it.

 

[andy2020]

I have the same bootleg! It also has the same connection between the pins on the PCM chip, except I do have the audio glitches you mention. Perhaps I should make the connection better!

It's on high address lines. I can't imagine why this hack would be needed, instead of just addressing the needed memory via the game ROM.

 

[shadowkn55]

The hack is done so the address decoder for the V-ROMs can access 4mbit eproms. The smallest rom size when using the jumpers is 8mbit.