Mapper type?

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Mapper type?
by on (#6605)
I found a weird unlicenced game named "Olympic I.Q." by Sachen, i'm trying to figure out which mapper it's using. it has 32k PRG-ROM (27C512) and (at the moment) unknown size of VROM, mapper itself is a 74LS374. Could this be a CNROM (VROM switch) clone?
- sepi

by on (#6610)
That would be iNES mapper #243 - the "74LS374N" mapper is NOT a 74LS374, but a custom mapper chip labeled "74LS374N" to deliberately mislead anyone who might want to dump the game or create duplicate cartridges.

Incidentally, the PRG ROM is 64KB and CHR ROM is 32KB.

by on (#6658)
Hmm, i thought that 27C512 was size of 32kB...

Is there any information available from this custom chip? (i couldn't find any) is it a just plain mapper? or does it have some sort of encryption scheme? :) i'm planning to remove chips from the board and dumping them with EEPROM tool.

by on (#6662)
The chip functions similarly to an MMC3, with registers at $4100 and $4101 (and 4300/4301, 4500/4501, ..., 5D00/5D01, 5F00/5F01). It is NOT a plain mapper, though Sachen certainly wanted you to think so (and cause you to produce a nonfunctioning cartridge). For the record, Olympic IQ has been dumped by Kevin Horton, though I don't know if the ROM image is in circulation.

A 27C512 is 512Kbit, or 512 / 8 = 64KB.

by on (#6692)
Well, i have to admit that the Sachen has really used a quite unusual copyright protection scheme here:wink:

Thank you very much, Quietust.