(r) this line goes to the ROM only.
(s) this line is Shared between the ROM, MMC/chip, and Nintendo
(n) this line connects to the NES cart edge only, and not the ROM
(w) this line connects to the WRAM only and nowhere else


MMC3 Chip:    (44 pin QFP) [Made by Kevin Horton (khorton@iquest.net)]
----------
Comes in three types: 'MMC3A', 'MMC3B', and 'MMC3C'

                           33     23
                            |     |
                           .-------.
                        34-|       |-22
                           | MMC3B |
                        44-|       |-12
                           \-------'
                            |     |
                            1     11


Pin# Function      Pin# Function
---- --------      ---- --------

1  - ??? *1        23 - PRG A17 (r)
2  - CHR A10 (r)   24 - PRG A13 (n)
3  - CHR A12 (n)   25 - PRG A18 (r)
4  - CHR A11 (n)   26 - PRG /CE (r)
5  - CHR A10 (n)   27 - +5V
6  - GND           28 - GND
7  - CHR A13 (r)   29 - M2
8  - CHR A14 (r)   30 - WRAM /CE (w)
9  - CHR A12 (r)   31 - PRG D7 (s)
10 - CIRAM A10 (n)*32 - PRG A0 (s)
11 - CHR A15 (r)   33 - PRG D6 (s)
12 - CHR A17 (r)   34 - PRG D0 (s)
13 - /IRQ          35 - PRG D5 (s)
14 - PRG /CE (n)   36 - PRG D1 (s)
15 - GND           37 - PRG D4 (s)
16 - ??? *2        38 - PRG D2 (s)
17 - PRG R/W (n)   39 - PRG D3 (s)
18 - PRG A15 (r)   40 - GND
19 - PRG A13 (r)   41 - WRAM CE (w)
20 - PRG A14 (n)   42 - WRAM /WE (w)
21 - PRG A16 (r)   43 - CHR A11 (r)
22 - PRG A14 (r)   44 - CHR A16 (r)

NOTES:

*:  On Gauntlet, this is unused.


*1: PINS 1 & 2.  Sometimes these are connected together.  If they are not,
pin 1 is left floating.

*2: PIN 16. Sometimes this is connected to ground.  Other times it is left
floating.  

It seems that pins 1,2 & 16 are related; pins 1 & 2 are shorted as are pins
15 and 16.  Or else pisn 1 & 2 are left open as well as 15 & 16.  I've never
seen say, pins 1 & 2 shorted while pin 16 was open or vice-versa.  I suspect
they relate to extra RAM in the CHR section.