72 pin SIMM Pinout

[30-pin SIMM] [72-pin SIMM] [72-pin SODIMM] [72-pin ECC SIMM]
[Memory Module Signal Assignments]

72 pin SIMM modules are obsolete and no longer used. SIMM modules were replaced by DIMM memory modules.
The pinout for 72 pin SIMM memory is listed in the table below.

72-pin memory modules have been obsolete for some time now. 72-pin memory modules should not be used in new designs.
Refer to the main Computer Memory Modules page for an updated listing of current memory module formats.

DDR/DDR2 formats are in mass production, refer to Memory Module manufacturers page for detailed coverage.

The 72-pin SIMM pin out table describes an outdated memory module which is no longer in production.
SIMM memory is obsolete and should be replaced by DIMM modules in new systems.
The signal names or signal assignments and pin numbers are still valid, but relate to an out-dated memory stick

Single Inline Memory Module [SIMM]
Pin Non-Parity Parity Description
1 VSS VSS Ground
2 DQ0 DQ0 Data 0
3 DQ16 DQ16 Data 16
4 DQ1 DQ1 Data 1
5 DQ17 DQ17 Data 17
6 DQ2 DQ2 Data 2
7 DQ18 DQ18 Data 18
8 DQ3 DQ3 Data 3
9 DQ19 DQ19 Data 19
11 n/c n/c Not connected
12 A0 A0 Address 0
13 A1 A1 Address 1
14 A2 A2 Address 2
15 A3 A3 Address 3
16 A4 A4 Address 4
17 A5 A5 Address 5
18 A6 A6 Address 6
19 A10 A10 Address 10
20 DQ4 DQ4 Data 4
21 DQ20 DQ20 Data 20
22 DQ5 DQ5 Data 5
23 DQ21 DQ21 Data 21
24 DQ6 DQ6 Data 6
25 DQ22 DQ22 Data 22
26 DQ7 DQ7 Data 7
27 DQ23 DQ23 Data 23
28 A7 A7 Address 7
29 A11 A11 Address 11
31 A8 A8 Address 8
32 A9 A9 Address 9
33 /RAS3 /RAS3 Row Address Strobe 3
34 /RAS2 /RAS2 Row Address Strobe 2
35 n/c PQ3 Parity bit 3 (for the 3rd byte, bits 16-23)
36 n/c PQ1 Parity bit 1 (for the 1st byte, bits 0-7)
37 n/c PQ2 Parity bit 2 (for the 2nd byte, bits 8-15)
38 n/c PQ4 Parity bit 4 (for the 4th byte, bits 24-31)
39 VSS VSS Ground
40 /CAS0 /CAS0 Column Address Strobe 0
41 /CAS2 /CAS2 Column Address Strobe 2
42 /CAS3 /CAS3 Column Address Strobe 3
43 /CAS1 /CAS1 Column Address Strobe 1
44 /RAS0 /RAS0 Row Address Strobe 0
45 /RAS1 /RAS1 Row Address Strobe 1
46 n/c n/c Not connected
47 /WE /WE Read/Write
48 n/c n/c Not connected
49 DQ8 DQ8 Data 8
50 DQ24 DQ24 Data 24
51 DQ9 DQ9 Data 9
52 DQ25 DQ25 Data 25
53 DQ10 DQ10 Data 10
54 DQ26 DQ26 Data 26
55 DQ11 DQ11 Data 11
56 DQ27 DQ27 Data 27
57 DQ12 DQ12 Data 12
58 DQ28 DQ28 Data 28
60 DQ29 DQ29 Data 29
61 DQ13 DQ13 Data 13
62 DQ30 DQ30 Data 30
63 DQ14 DQ14 Data 14
64 DQ31 DQ31 Data 31
65 DQ15 DQ15 Data 15
66 n/c n/c Not connected
67 PD1 PD1 Presence Detect 1
68 PD2 PD2 Presence Detect 2
69 PD3 PD3 Presence Detect 3
70 PD4 PD4 Presence Detect 4
71 n/c n/c Not connected
72 VSS VSS Ground

SIMM Size & Access Time
PD1 PD2 PD3 PD4 Size Access time
GND GND - - 4 or 64 MB -
NC GND - - 2 or 32 MB -
GND NC - - 1 or 16 MB -
NC NC - - 8 MB -
- - GND GND - 50nS, 100nS
- - NC GND - 80nS
- - GND NC - 70nS
- - NC NC - 60nS

The edge connector pin-outs for the 72 PIN SIMM [Single Inline Memory Module] is listed in the table above.
The follow up tables provide the size and access times.

Notes: A9 is a N/C on 256k and 512k modules.
A10 is a N/C on 256k, 512k, 1M and 4M modules.
RAS1/RAS3 are N/C on 256k, 1M and 4M modules.
Data width is 32 bits per memory stick [the front 72 pins and back 72 fingers on the card are connected together]

72 Pin SIMM Memory Module Size

The approximate board size. 4.25" x 1.0"

SIMM: Single Inline Memory Module. SIMM's have pins on the front and back of the card, but they are connected together.
DRAM: Dynamic Random Access Memory
FPM:Fast Page Mode: (asynchronous) Obsolete, faster than normal DRAM, used in 386/486 computers.
EDO: Extended Data Out: (asynchronous) A superset of FPM, just faster than FPM.
All 72 pin SIMMs use either EDO or FPM memory. 72 pin SIMM modules are obsolete and no longer used.
72 pin SIMMs have an alignment notch on the bottom left to side, and a notch in the center of the PWB.
Additional 72 pin module pinouts
72 pin ECC SIMM pin out
72 pin SO DIMM pin out

Back to the main Computer Memory Modules information page. For electronic device manufacturers see one of these pages:
Memory IC manufacturers
Memory Module manufacturers
Additional electronic Equipment manufacturers may be found by selecting the OEM Equipment icon below, or component manufacturers may be found by selecting the Components icon below.
Also refer to an alphabetic listing of Companies that manufacture Components, listed in order.

Of course there is always a chance that you would need to interface to an existing design which uses 75-pin SIMMS.
Given the age of an operating SIMM module, implies it might be time for a little circuit debug.
The pin out shown above is fixed, no organization is working the SIMM standard any longer,
so the no-connect pins will never be connected or used for any purpose.
Therefore no-connect pins can be treated as non-existent.
The Electrical Standard, physical specification and interface details are all locked in place and will not change.

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Modified 2/5/12
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