Yamaha DX7 II cartridges. RAM4 and PF-2000 ROM.
The magical RAM4 cartridge.
This is the one you need to store your sound creations, able to store 64 voices and 32 performance patches.
A performance is just a voice with added controllability using the two parameter sliders and the utterly rediculous micro-tuning and fractional scaliing. Now that the RAM4 is over 30 years old, it could be time to replace the internal battery. The case easily splits into halves, front and back, by gently prising apart along the join line. The battery is a CR2430 with horizontal solder tags, it is available as a direct replacement if you search extremely hard and pay dubious suppliers, but by adapting the tags of a standard CR2430 the job is done. You could fit a CR2032 tagged cell which would be easier to locate and equally satisfactory. There is 6mm of height available to easily fit the battery. Only the RAM4 and RAM5 contain a battery, not the pre-programmed ROM cartridges.
The elusive PF-2000 cartridge.
This is my latest discovery, it was supplied with the PF-2000 electronic piano, which is a DX7IID internally.
The cartridge contains two banks of 32 performances and two banks of 64 voices. (64 performances and 128 voices). There are only 1 or 2 compatibility issues. First of all, the PF had a longer display so the DX7 display chops off the end of the performance names, but not the voice names, no major problem there. The other issue is that 4 of the performances have split keyboard applied, this is probably only relevant to the DX7S, which is mono timbral. The DX7S just plays one of the split sounds, no major problem there either. It's well worth getting this cartridge if you're good at finding unicorns, as the sounds are all useable and of good quality, with no foolish effects.
Below is the performance list of the PF-2000 cartridge.
Below is the performance list of the PF-2000 cartridge.