How would I VGM log an auto-scrolling shooter using MAME?

[SMS Alfredo]

I've been trying to rip a couple of songs from Cobra Command (specifically the side-scrolling arcade version) using the MAME VGM logging mod, and while the logging works perfectly, I've run into a couple of other problems.

Due to the nature of the game, it's always moving forward, which means I can't just let the emulator sit there and record the entirety of a song. Now my first thought would be to find a code online that'd allow me to access the game's sound test, if there even is one. But thanks to the game's relative obscurity, I couldn't find any. Same goes for invinciblity cheats too.

So, any idea of what I could do to get myself out of this delema?

[ctr]

My usual method for games that use a discrete sound CPU (like in this case) is to figure out how the main CPU communicates with the sound CPU.

Open the MAME source code and look for "sound latch" or similar, often you'll get the memory address. In this case, it's here.

Then run MAME with the debugger enabled (mame64 -d cobracom), halt the main CPU early (usually by crashing it as soon as it starts), and you'll be able to send commands to the sound CPU without any interference.

I got music to play by entering this:

Code: Select all

pc=8124
g
b@3e00=1f

This might sound complicated but it really isn't.