
The dat contains already checksums for the roms without header and with clrmame you use a special header xml file that tells clrmame to ignore the first 16 bytes when calculating crc32 and stuff, which is in fact the header.
There could be roms without headers, but then each emulator would need an internal list which game uses what mapper (afaik Nestopia does this).
The other "problem" with NES roms is that they contain different types of roms for a single game, like a PRG and CHR rom, but No-Intro only uses the combined romdata.
Anyway, back to PS3.
The decrypted files do not retain any of the original structure of the medium it was read from. And that is the real problem.
