PC10 ROM-Images

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Playchoice 10 ROM-Images can be stored in two formats:

iNES Format

PC10 games in iNES format are indicated by Bit1 of Byte 7 of the iNES header. If the flag is set, then the file should contain some additional entries after the PRG ROM and CHR ROM areas:

  • 8Kbyte INST ROM (containing data and Z80 code for instruction screens)
  • 16 bytes RP5H01 PROM Data output (needed to decrypt the INST ROM)
  • 16 bytes RP5H01 PROM CounterOut output (needed to decrypt the INST ROM) (usually constant: 00,00,00,00,FF,FF,FF,FF,00,00,00,00,FF,FF,FF,FF)

The two required PROM sections are missing in older ROM-images. A tool for upgrading such incomplete dumps can be found at http://nocash.emubase.de/pc10make.zip

Note: Some very old ROM-images don't have the PC10 flag set in the header, and, instead, they declare the 8K INST ROM as an additional VROM bank.

MAME Format

Instead of using a single ROM-image file, MAME stores all ROMs, EPROMs, and PROMs chips in separate files.

The PROM data is typically stored in a file called "security.prm". It contains only the 16 Data bytes (not the CounterOut bytes). All bits in the PROM file are inverted, and the bit ordering is reversed: bit0 (the first bit of the PROM's serial bit-stream) is stored in bit7 of the 1st byte of the file).

PC10 Emulators

The iNES format is used by no$nes. The MAME format is used by MAME.

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