"Machine 1" as it's called in the current source is actually a later version of the P3. It has the PSU and voltage regulator cards, 64K DRAM card, 8085 CPU card, floppy controller card, video/keyboard interface card with the later char ROM
"Machine 2" has the earlier char ROM and the DRAM split across a 48K and a 16K card.
The keyboard ROMs contain the same code but come from different ICs (8278 vs. 8041).
So they're neither marketed as two different machines nor is the newer char ROM an add-on option - hence I thought switching the complete sets as "BIOS" was appropriate.
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