diff --git a/src/emu/cpu/pps4/pps4.c b/src/emu/cpu/pps4/pps4.c
index 98a9bfdb6a6..ddcd2501189 100644
--- a/src/emu/cpu/pps4/pps4.c
+++ b/src/emu/cpu/pps4/pps4.c
@@ -27,6 +27,33 @@
  *
  *   Note: External clock should be divided by 18 (not implemented).
  *
+ *   Pinouts:
+ *              10660                               11660
+ *
+ *      +--------\  /--------+              +--------\  /--------+
+ *  1  [| DIB-3   ++  DIA-3  |]  42     1  [| DIO-4       DIO-3  |]  42
+ *  2 [-| DIA-2       DIB-4  |-] 41     2 [-| DIA-4       DIO-2  |-] 41
+ *  3  [| DIB-2       DIA-4  |]  40     3  [| DIA-3       DIO-1  |]  40
+ *  4 [-| DIA-1       NC     |-] 39     4 [-| DIA-2       Vdd    |-] 39
+ *  5  [| DIB-1       A/B-1  |]  38     5  [| DIA-1       A/B-1  |]  38
+ *  6 [-| Vdd         A/B-2  |-] 37     6 [-| I/O-5       A/B-2  |-] 37
+ *  7  [| I/D-5       A/B-3  |]  36     7  [| I/O-6       A/B-3  |]  36
+ *  8 [-| I/D-6       A/B-4  |-] 35     8 [-| I/O-7       A/B-4  |-] 35
+ *  9  [| I/D-7       A/B-5  |]  34     9  [| I/O-8       A/B-5  |]  34
+ * 10 [-| I/D-8       A/B-6  |-] 33    10 [-| I/O-1       A/B-6  |-] 33
+ * 11  [| I/D-1       A/B-7  |]  32    11  [| I/O-4       A/B-7  |]  32
+ * 12 [-| I/D-4       A/B-8  |-] 31    12 [-| I/O-2       A/B-8  |-] 31
+ * 13  [| I/D-2       A/B-9  |]  30    13  [| I/O-3       A/B-9  |]  30
+ * 14 [-| I/D-3       A/B-10 |-] 29    14 [-| W/IO        A/B-10 |-] 29
+ * 15  [| W/IO        A/B-11 |]  28    15  [| CLK ~B      A/B-11 |]  28
+ * 16 [-| CLK ~B      A/B-12 |-] 27    16 [-| CLK A       A/B-12 |-] 27
+ * 17  [| CLK A       NC     |]  26    17  [| VCLK        DO-4   |]  26
+ * 18 [-| PO          DO-3   |-] 25    18 [-| Xtal1       DO-3   |-] 25
+ * 19  [| SPO         DO-4   |]  24    19  [| Xtal2       DO-2   |]  24
+ * 20 [-| DO-2        NC     |-] 23    20 [-| Vss         DO-1   |-] 23
+ * 21  [| DO-1        Vss    |]  22    21  [| SPO         TC1-14 |]  22
+ *      +--------------------+              +--------------------+
+ *
  *****************************************************************************/
 #include "emu.h"
 #include "debugger.h"