MMC3 pinout

Nintendo MMC3: 44-pin QFP (Canonically mapper 4)

                             / \
                            / O \
                      ? -> /01 44\ -> CHR A16 (r)
           (r) CHR A10 <- /02   43\ -> CHR A11 (r)
          (n) PPU A12 -> /03     42\ -> PRG RAM /WE (w)
         (n) PPU A11 -> /04       41\ -> PRG RAM +CE (w)
        (n) PPU A10 -> /05         40\ -- GND
               GND -- /06         \ 39\ <- CPU D3 (nrw)
      (r) CHR A13 <- /07           \ 38\ <- CPU D2 (nrw)
     (r) CHR A14 <- /08         \  _\ 37\ <- CPU D4 (nrw)
    (r) CHR A12 <- /09         \ \|    36\ <- CPU D1 (nrw)
 (n) CIRAM A10 <- /10           \ \     35\ <- CPU D5 (nrw)
  (r) CHR A15 <- /11         \  _\    o  34\ <- CPU D0 (nrw)
  (r) CHR A17 <- \12       /\ \|         33/ <- CPU D6 (nrw)
      (n) /IRQ <- \13        \ \        32/ <- CPU A0 (nrw)
    (n) /ROMSEL -> \14   /    \        31/ <- CPU D7 (nrw)
             GND -- \15  |_   /       30/ -> PRG RAM /CE (w)
                ? -> \16   |         29/ <- M2 (n)
           (n) R/W -> \17  |/       28/ -- GND
        (r) PRG A15 <- \18         27/ -- VCC
         (r) PRG A13 <- \19       26/ -> PRG /CE (r)
          (n) CPU A14 -> \20     25/ -> PRG A17 (r)
           (r) PRG A16 <- \21   24/ <- CPU A13 (n)
            (r) PRG A14 <- \22 23/ -> PRG A18 (r)
                            \ O /
                             \ /

01 sometimes shorted to pin 2, otherwise floating
16 sometimes grounded, otherwise floating
 No behavior is known to change as a result of these wiring variations

Note the orientation of the text: "MMC3" when viewed upright specifies pin 1 is bottom face, leftmost.

Mappers 37 and 47 connect pins 42 and 30 to a 74161

iNES Mapper 118 connects pin 12 to CIRAM A10, and pin 10 is n/c.

iNES Mapper 119 connects pin 44 to a 7432 and to the CHR RAM's +CE pin.