INES Mapper 065

iNES Mapper 065 refers to games that use Irem’s H3001 mapper.

Disch’s older documentation is known to be wrong, incorrectly believing in a changeable bank at $C000. It doesn’t exist, see [1]

 Known Games:
 --------------------------
 Daiku no Gen San 2
 Kaiketsu Yanchamaru 3
 Spartan X 2

 Registers:
 --------------------------
   Mask: $F007  

   $8000-$8007:  PRG Reg 0 (8k @ $8000 -or- 8k @ $C000)
   $A000-$A007:  PRG Reg 1 (8k @ $A000)

   $B000-$B007:  CHR regs

   $9000:  [X... ....]  PRG bank layout
     Very similar to VRC4 or MMC3
     %0 = bank at $8000 set by writes to $8000, bank at $C000 always $3E
     %1 = bank at $C000 set by writes to $8000, bank at $8000 always $3E

     bank at $E000 always $3F

   $9001:  [MM.. ....]  Mirroring
     %00 = Vert
     %10 = Horz
     %01,%11 = 1scA

   $9003:  [E... ....]  IRQ Enable (0=disabled, 1=enabled)
   $9004:  [.... ....]  Reload IRQ counter
   $9005:  [IIII IIII]  High 8 bits of IRQ Reload value
   $9006:  [IIII IIII]  Low 8 bits of IRQ Reload value

 On Powerup:
 ---------------------------
 On powerup, it appears as though PRG regs are inited to specific values:

   $8000 = $00
   $A000 = $01

 Games do rely on this and will crash otherwise.

 CHR Setup:
 ---------------------------

       $0000   $0400   $0800   $0C00   $1000   $1400   $1800   $1C00 
     +-------+-------+-------+-------+-------+-------+-------+-------+
     | $B000 | $B001 | $B002 | $B003 | $B004 | $B005 | $B006 | $B007 |
     +-------+-------+-------+-------+-------+-------+-------+-------+

 IRQs:
 ---------------------------

 This mapper's IRQ system is very simple.  There's a 16-bit internal down counter which (when enabled),
 decrements by 1 every CPU cycle.  When the counter reaches 0, an IRQ is fired.  The counter stops at 0 -- it
 does not wrap and isn't automatically reloaded.

 Any write to $9003 or $9004 will acknowledge the pending IRQ.

 Any write to $9004 will copy the 16-bit reload value into the counter.

 $9006 and $9005 set the reload value, but do not have any effect on the actual counter.  Note that $9005 is
 the HIGH bits, not the low bits.

INES Mapper 065

See also