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FastROM

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FastROM is 3.58 MHz and its ROM access speed is 120ns. It is about 33% faster than SlowROM. FastROM is a property of the ROM chip itself and not the board it is soldered onto.[2] When the 5A22 is operating at fastROM speed, there are 6 master clock cycles per CPU machine cycles.

FastROM speeds only apply to the upper halves of banks $80-bf and all of banks $c0-ff.[1]

The SAS cannot use FastROM.[3] Games which utilize fastrom should indicate this at bit 4 of FFD5 of the cartridge header.[4]

master clock divider speeds.png

See Also

External Links

References

  1. Near, https://forums.nesdev.org/viewtopic.php?t=9585
  2. Bregalad, lbid.
  3. caution 3.3.6.1 on page 1-3-4 of Book II of the official Super Nintendo development manual
  4. http://problemkaputt.de/fullsnes.htm#snesmemorycontrol