Quoted from ForceFlow:
A system 80B can accept a 2764 EPROM. Shouldn't there be enough room for the ROM file on that EPROM?
Or is the memory restriction the result of something else?
It's a little bit more complex than that:
Basically, the SYS 80B system herits the SYS 80/80A architecture, and the address bus is only decoded on 14 bits (while 6502 has a 16 bits wide address bus).
The 2764 PROM1 is decoded at $2000-$3FFF (8 KB). The 2716 PROM2 is decoded at $1000-$17FF (2KB). So the maximum ROM space is initially limited to 10 KB (8 + 2).
On early SYS80B, only the 2764 was used, because the programs were quite simple, and display few messages.
Then, as programs evolves, it used more and more messages, and they needs to add the 2716 to store all the code.
But this was still not enough... on later SYS80B, they decided to use a 2732 in place of 2716, so extending the ROM area to 12 KB (8 + 4). But to achieve that, they connect an additional wire at A15 signal to the 2732. Thus, the first 2 KB of the 2732 is decoded at $1000-$17FF and the upper 2 KB at $9000-$97FF.
There is no way to easily add an extended memory, because of this (crazy) partial decoding on 14 bits (+ A15 but only for 2732).
So the maximum memory space is definitely limited to 12 KB and cannot be extended.
On latest SYS80B, the 12 KB space is fully used ! The "Bone Busters Inc." use all available memory (both 2764 + 2732 space) and there is no place where to store any additional code. On "Bad Girls", the English release has just enough free space to insert the patch. But, on French and German releases, as the messages are a little bit longer, they use more memory and let not enough free space for the patch !!! so the patch is only possible on English release.
Fortunately, we have always found enough free space in PROM1 for all SYS80B to install our FREEPLAY patch. Thus, you only need to program the 2764 and never the 2716/2732.
For "Bad Girls French/German" and "Bone Busters Inc.", we also study the possibility to store the patch somewhere in the 2732, but it's not possible (both 2764 and 2732 are fully filled).
Technically, the patch is possible and ready to install (it's very similar to others SYS80B), but there is no place to store it on those two models.