The connector is 3 rows (A, B, & C) by 32 columns. These are marked well, except for the 2Mb board. Put it chip-side down, connector at the bottom. The solder pads for the connector on the circuit board now have pin A1 in the lower lefthand corner, something like this:

                            Solder Side
C1 oooooooooooooooooooooooooooooooo C32
B1 oooooooooooooooooooooooooooooooo B32
A1 oooooooooooooooooooooooooooooooo A32
---------------------------------------------------
                            Connector 
    ----------------------------------------------

We are mainly interested in pins A17 & A32, wired on all Model 80 types, & pins A16 & A18, N/Cs on the Type 1 planars, wired for the Type 2 and 3 planars. An 'x' on the chart means the pin is tied to ground.

      A16    A17    A18    A32
1Mb           x             x
2Mb           x
4Mb   x       x      x

   This explains why the 4Mb modules are treated as 2Mb in a Type 1 planar. I don't know if any of the presence detects signify memory speed. The chart above shows the newer 2Mb board. Another surprise is the little memory cards that go on the @FAFF.ADF 2 - 6Mb 386 Memory expansion board are the same pinouts. Of course each board is 2Mb & the presence detect is the same as above. I don't believe this board was offered in any other capacity. You can use one of these little cards on the planar, although it has to be in the slot furthest from the power supply due to the keying & right-angle of the connector. At least the chips are conventional & marked as 85nS.

Pinouts: (If all pinouts could be this simple; If all connectors wouldn't be
this proprietary)
 

A1:    Reserved A2:    -Mem Write A3:    Address 0 A4:    Address 1 A5:    Address 2 A6:    Address 3 A7:    Address 4 A8:    Address 5 A9:    Address 6 A10:    Address 7 A11:    Address 8 A12:    -Row Address Strobe 0 A13:    -Row Address Strobe 1 A14:    -Row Address Strobe 2 A15:    -Row Address Strobe 3 A16:    Presence Detector (N/C on Type 1) A17:    Presence Detector A18:    Presence Detector (N/C on Type 1) A19:    -Column Address Strobe 0 A20:    -Column Address Strobe 1 A21:    -Column Address Strobe 2 A22:    -Column Address Strobe 3 A23:    Data Parity 0 A24:    Data Parity 1 A25:    Data Parity 2 A26:    Data Parity 3 A27:    -Byte Enable 0 A28:    -Byte Enable 1 A29:    -Byte Enable 2 A30:    -Byte Enable 3 A31:    -Column Address Strobe Parity A32:    Presence Detector

B1:    Ground  B2:    +5VDC B3:    Ground B4:    +5VDC B5:    Ground B6:    +5VDC B7:    Ground B8:    +5VDC B9:    Ground B10:    +5VDC B11:    Ground B12:    +5VDC B13:    Ground B14:    +5VDC B15:    Ground B16:    +5VDC B17:    Ground B18:    +5VDC B19:    Ground B20:    +5VDC B21:    Ground B22:    +5VDC B23:    Ground B24:    +5VDC B25:    Ground B26:    +5VDC B27:    Ground B28:    +5VDC B29:    Ground B30:    +5VDC B31:    Ground B32:    +5VDC

C1:    Data 0  C2:    Data 1 C3:    Data 2 C4:    Data 3 C5:    Data 4 C6:    Data 5 C7:    Data 6 C8:    Data 7 C9:    Data 8 C10:    Data 9 C11:    Data 10 C12:    Data 11 C13:    Data 12 C14:    Data 13 C15:    Data 14 C16:    Data 15 C17:    Data 16 C18:    Data 17 C19:    Data 18 C20:    Data 19 C21:    Data 20 C22:    Data 21 C23:    Data 22 C24:    Data 23 C25:    Data 24 C26:    Data 25 C27:    Data 26 C28:    Data 27 C29:    Data 28 C30:    Data 29 C31:    Data 30 C32:    Data 31

Peter Wendt shows a strong habit of too much time...
   How about that comparison chart below ? I once made it to build a
"Mod.80-to-72pin" converter - an attempt that failed so far, by various
reasons. (Lack of time mostly)

PIN-OUT COMPARISON CHART 
       IBM PS/2 Mod 80                    IBM PS/2 Mod. 70 
       Memory Daughter Card               72-pin SIMM 
A01   NA    Reserved 
A02   O     -Memory Write         Write Enable        O   47 
A03   O     -MA 0                 Adress 0            O   12 
A04   O     -MA 1                 Adress 1            O   13 
A05   O     -MA 2                 Adress 2            O   14 
A06   O     -MA 3                 Adress 3            O   15 
A07   O     -MA 4                 Adress 4            O   16 
A08   O     -MA 5                 Adress 5            O   17 
A09   O     -MA 6                 Adress 6            O   18 
A10   O     -MA 7                 Adress 7            O   28 
A11   O     -MA 8                 Adress 8            O   31 
A12   O     -RAS 0                RAS 0               O   44 
A13   O     -RAS 1                RAS 1               O   45 
A14   O     -RAS 2                RAS 2               O   34 
A15   O     -RAS 3                RAS 3               O   33 
A16   O     -RAMHS (Type 3) 1
A17   O     -R (Mod. inst.) 2
A18   O     T2     (Type 3) 3
A19   O     -CAS 0                CAS 0               O   40 
A20   O     -CAS 1                CAS 1               O   43 
A21   O     -CAS 2                CAS 2               O   41 
A22   O     -CAS 3                CAS 3               O   42 
A23   IO    -MPD 0                Parity Data 0       IO  36 
A24   IO    -MPD 1                Parity Data 1       IO  37 
A25   IO    -MPD 2                Parity Data 2       IO  35 
A26   IO    -MPD 3                Parity Data 3       IO  38 
A27   O     -BE 0                 Block Select 0      O   29 
A28   O     -BE 1                 Block Select 1      O   46 
A29   O     -BE 2                 Block Select 2      O   66 
A30   O     -BE 3                 Block Select 3      O   71 
A31   O     -CASP                 -CAS P              O   11 
A32   O     T1 (Mod. Size) 4
B01   NA    Ground                Ground              NA   1 
B02   O     +5VDC                 +5VDC               O   10 
B03   NA    Ground                Ground              NA  39 
B04   O     +5VDC                 +5VDC               O   30 
B05   NA    Ground                Ground              NA  72 
B06   O     +5VDC                 +5VDC               O   59 
B07   NA    Ground 
B08   O     +5VDC 
B09   NA    Ground 
B10   O     +5VDC 
B11   NA    Ground 
B12   O     +5VDC 
B13   NA    Ground 
B14   O     +5VDC 
B15   NA    Ground 
B16   O     +5VDC 
B17   NA    Ground 
B18   O     +5VDC 
B19   NA    Ground 
B20   O     +5VDC 
B21   NA    Ground 
B22   O     +5VDC 
B23   NA    Ground 
B24   O     +5VDC 
B25   NA    Ground 
B26   O     +5VDC 
B27   NA    Ground 
B28   O     +5VDC
B29   NA    Ground
B30   O     +5VDC 
B31   NA    Ground 
B32   O     +5VDC 
C01   IO    Data 00               Data 00             IO   2 
C02   IO    Data 01               Data 01             IO   4 
C03   IO    Data 02               Data 02             IO   6 
C04   IO    Data 03               Data 03             IO   8 
C05   IO    Data 04               Data 04             IO  20 
C06   IO    Data 05               Data 05             IO  22 
C07   IO    Data 06               Data 06             IO  24 
C08   IO    Data 07               Data 07             IO  26 
C09   IO    Data 08               Data 08             IO  49 
C10   IO    Data 09               Data 09             IO  51 
C11   IO    Data 10               Data 10             IO  53 
C12   IO    Data 11               Data 11             IO  55 
C13   IO    Data 12               Data 12             IO  57 
C14   IO    Data 13               Data 13             IO  61 
C15   IO    Data 14               Data 14             IO  63 
C16   IO    Data 15               Data 15             IO  65 
C17   IO    Data 16               Data 16             IO   3 
C18   IO    Data 17               Data 17             IO   5 
C19   IO    Data 18               Data 18             IO   7 
C20   IO    Data 19               Data 19             IO   9 
C21   IO    Data 20               Data 20             IO  21 
C22   IO    Data 21               Data 21             IO  23 
C23   IO    Data 22               Data 22             IO  25 
C24   IO    Data 23               Data 23             IO  27 
C25   IO    Data 24               Data 24             IO  50 
C26   IO    Data 25               Data 25             IO  52 
C27   IO    Data 26               Data 26             IO  54 
C28   IO    Data 27               Data 27             IO  56 
C29   IO    Data 28               Data 28             IO  58 
C30   IO    Data 29               Data 29             IO  60 
C31   IO    Data 30               Data 30             IO  62 
C32   IO    Data 31               Data 31             IO  64 
                                   Reserved           NA  19 
                                   Reserved           NA  32 
                                   Reserved           NA  48 
                                   PD 0               I   67 
                                   PD 1               I   68 
                                   PD 2               I   69 
                                   PD 3               I   70 
Notes:
#1) Contact is tied to GND if the module is High Speed (80ns)
#2) Contact is tied to GND to signal installed module
#3) If T1=NC and T2=GND the module is 4MB (25MHz-boards only)
#4) If T1=GND and R=GND the module is 1MB (16MHz boards only)
         If T1=NC  and R=GND there is a 2MB module installed (20Mhz only)
         T2 is not present on 16 & 20MHz platforms and may not be used

PS/2 Model 80 Presence Detection - Possible Combinations
+--+---+---+--------------------------------------------+
 R  T1  T2   Module Presence / Type Pins 
+--+---+---+--------------------------------------------+
 NC  X   X    No module present in 
 G   G   X    1MB module installed (16MHz planar) 
 G   NC  X    2MB module installed (20MHz planar) 
 G   NC  G    4MB module installed (25MHz planar) 
+--+---+---+--------------------------------------------+

PS/2 Model 70 Presence Detection - Possible Combinations

 7 6 6 6 
 0 9 8 7  <---- Module Pins
+-+-+-+-+-------------------------------------------+
 3 2 1 0   Presence Detect Value 
+-+-+-+-+-------------------------------------------+
 - - - -   No module present    (All planars) 
 G G - G   1 MB / 100ns Parity  (Type 1 planar only) 
 G G G -   2 MB / 100ns Parity  (Type 1 planar only) 
 G - - G   1 MB /  85ns Parity  (Type 1 + 2 planar) 
 G - G -   2 MB /  85ns Parity  (Type 1 + 2 planar) 
 - G G -   2 MB /  80ns Parity  (Type 3 + 4 planar) 
+---+---+---+---+-----------------------------------+
 R1  R2         <---- Memory coding on original IBM-modules

Type 1 are the full lenght 16 and 20MHz planars
Type 2 are the reduced lenght 16 and 20MHz planars
Type 3 is the 25MHz 386 planar
Type 4 is the 25MHz 486 planar

G = GND measured against Pin 72 (module GND)
- = open connection measured against Pin 72