Telling apart HiROM and LoROM / FastROM and SlowROM SNES games?

GuntzGuntz
in The Brewery
I've been comparing games and ROM header readouts and I still can't figure out how to identify a hi or lo ROM board just by looking at it. I thought HiROM used MAD-1 and LoROM used some generic logic chip, but I don't think that's the case.



Are there any tell tale signs or do you always have to go by what the ROM's header says?



Also, are fast and slow roms of any significance? Do they add PCB differences or is it just a software thing?

Comments

  • josete2kjosete2k
    Basically



    SHVC-xAxx-xx LoRom

    SHVC-xJxx-xx HiRom



    All HiRom are FASTROM, LoRom can be Slowrom (200ns) or Fastrom (120ns).



    If you're going to make repros, make sure you buy 100F EPROM.
  • GuntzGuntz
    What do MAD-1 and those various generic logic chips do then? Do they perform the same function?
  • josete2kjosete2k
    Generic chips, 74LS139 ie, are decoders and are used to access the entire rom and sram.



    MAD-1 has the same function plus the battery operating logic control.



    I mean...



    With 139 the sram is always pluged by the battery.



    With MAD-1, when you power on your console, sram takes its energy from the snes, and only takes it from the battery when you power off your console.



    I hope you understand... my english is very poor.
  • GuntzGuntz
    No, that makes sense to me. Very interesting function the MAD-1 can do, never even knew about that. That probably greatly effects the battery's lifespan.



    So HiROM and LoROM are strictly ROM-to-cart-edge logic differences, right?
  • josete2kjosete2k
    LoRom hasn't got A15 and all adresses from A15 to A22 are different in HiRom/ LoRom



    LoRom's A16 is HiRom's A15

    ...

    LoRom's A20 is HiRom's A19

    ...
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