ROM SIMM Pinout

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This page shall contain ROM SIMM Pinouts.

Motorola 680×0 64-Pin ROM SIMM

This pinout applies to the Macintosh IIfx, IIci, IIsi and SE/30. If you have a different 680×0 Mac with a 64-pin SIMM slot, it is likely to use this pinout as well. If you use this pinout to construct an actual ROM SIMM, please take note that address bits should be offset by 2. For example, on your ROM chips, A0 should be connected to A2 in this pinout. A1 goes to A3, etc. This is because the ROM SIMM puts out 32-bits of data for each address, whereas each actual address is 8 bits of data. Skipping the first two bits effectively divides the address by 4. Forum member trag (Jeff Walther) has provided this information:

According to TGTTMFH:

ROM SIMM Socket

Pin Number          Signal Name
1                          +5V
2                          A0
3                          A1
4                          A2
5                          A3
6                          A4
7                          A5
8                          A6
9                          A7
10                        GND
11                        ROM CS_ 
12                        ROM OE_
13                        +5
14                         D0
15                         D1
16                         D2
17                         D3
18                         D4
19                         D5
20                         D6
21                         D7
22                         D8
23                         D9
24                         D10
25                         D11
26                         D12
27                         D13
28                         D14
29                         D15
30                         GND
31                         A8
32                         A9
33                         A10
34                         A11
35                         A12
36                         A13
37                         A14
38                         A15
39                         A16
40                         A17
41                         A18
42                         A19
43                         A20
44                         A21
45                         A22
46                         +5V
47                         D16
48                         D17
49                         D18
50                         D19
51                         D20
52                         D21
53                         D22
54                         D23
55                         D24
56                         D25
57                         D26
58                         D27
59                         D28
60                         D29
61                         D30
62                         D31
63                         +5V
64                         GND

PowerPC 160-Pin ROM SIMM

This is the pinout for Apple's (mostly) universal firmware module. As far as I can tell it was used from the NuBus Powermacs through the Beige G3 in their main professional machines. The consumer (LC/Performa) machines had other arrangements.

Disclaimer: I'm not responsible if you use this information to damage something or otherwise screw up. I might have made mistakes typing this. I might be insane. This pinout seemed to work for me. Keep in mind the effect hours with a multimeter, a couple of firmware modules and some ROM datasheets is likely to have had on my mental stability.

Power Surge (PS) is the generic name for the 7500, 8500, 9500 and clones and later family models. The 7200 uses the same ROM (yes, and the same code) and the same firmware module as the PS.

The Apple Network Server uses the same type of Firmware module as the Power Surge, though with different contents in the chips, of course. The prototypes of the PEX (PM9700) also use this ROM module, with still different code on the chips.

The voltage supply pins of the Beige G3 are different from the earlier modules because the Beige G3 uses a 3.3V supply and the earlier machines use a 5V supply. As far as I know the Beige G3 is the only machine that uses the 3.3V supply configuration. All the other machines, including the PEX using the 5V supply configuration.

The pins of Apple's universal firmware module are numbered 1 through 160. There are 80 on each side. Usually modules will have some numbers silk screened on them to help you out. The module is a DIMM. Every pin is unique. Pins on opposite sides of the board are not connected the way they are on SIMMs.

From edge to notch to notch to edge, they go 1 - 30, 31 - 55, 56 - 80, flip sides, 81 - 110, 111 - 135 and 136 - 160.

The first column in the list below is the Beige pin. The second column is the Power Surge (PS) pin. I have not explicitly mapped out all the pins on the NuBus Mac ROM module, but I would expect the pinout to be very similar if not identical to the Power Surge pinout. I have confirmed that it follows the same basic pattern.

The firmware module is 64 bits wide. On early machines this is usually achieved with four 16 bit wide storage chips, although larger numbers of narrower chips were sometimes used. On the Beige G3 there are just two 32 bit wide ROM chips. No one makes anything like that anymore (32 bit wide non-volatile memory chips).

The HL, HH, LL and LH designations on the Power Surge data pins refer to which ROM chip those data pins connect to. So, for example, you'll find four ROM chips on the motherboard labeled with those four designators. The D0 HL pin in the ROM socket connects to the D0 pin on the HL ROM chip which is soldered to the motherboard. In the X500 series, chip 341S0171 = LL, 341S0170 = LH, 341S0169 = HL and 341S0168 = HH. In the Kansas: 341S0380 = HH, 341S0381 = HL, 341S0382 = LH, 341S0383 = LL.

On the original G3 ROM (revision A) 341S0402 = H and 341S0403 = L.

There is no ROM soldered to the motherboard, but the Beige G3 uses two 32 bit wide ROM chips. The L and H refer to the high and low ROM chips.

More notes at the bottom.

Pin 	Beige       PS
1       NC         Vcc
2       GND        GND
3       Vpp?       Vpp?  (this would be used on a programmable module with old EEPROMs)
4       D16 L       D0 HL
5       D17 L       D1 HL
6       D18 L       D2 HL
7       D19 L       D3 HL
8        Vcc       N/A
9        NC       Vcc
10       Vcc       NC
11       D20 L       D4 HL
12       D21 L       D5 HL
13       D22 L       D6 HL
14       D23 L       D7 HL
15       GND       GND
16       D24 L       D8 HL
17       D25 L       D9 HL
18       D26 L       D10 HL
19       D27 L       D11 HL
20       Vcc       NC
21       NC       Vcc
22       NC?       NC
23       D28 L       D12 HL
24       D29 L       D13 HL
25       D30 L       D14 HL
26       D31 L  D15 HL
27       GND       GND
28       NC?       NC
29       NC?       NC
30       A2       A2
31       A4       A4
32       A6       A6
33       A8       A8
34       A10      A10
35       NC       NC
36       NC       NC
37       WE      WE (For programmable modules, also may connect to pin 117)
38       OE H       OE A1L   (May also connect to pin 118)
39       NC       NC
40       Vcc       NC
41       NC       Vcc
42       NC       NC
43       GND       GND
44       A12       A12
45       A14       A14
46       A16       A16
47       A18       A18
48       NC       NC
49       NC       NC
50       NC       NC
51       NC       NC
52       NC       NC
53       GND       GND
54       D16 H       D0 HH
55       D17 H       D1 HH
56       D18 H       D2 HH
57       D19 H       D3 HH
58       GND       GND
59       NC       Vcc
60       NC       NC
61       D20 H       D4 HH
62       D21 H       D5 HH
63       D22 H       D6 HH
64       D23 H       D7 HH
65       GND       GND
66       D24 H       D8 HH
67       D25 H       D9 HH
68       D26 H       D10 HH
69       D27 H       D11 HH
70       Vcc       NC
71       NC       Vcc
72       NC       NC
73       D28 H       D12 HH
74       D29 H       D13 HH
75       D30 H       D14 HH
76       D31 H       D15 HH
77       GND       GND
78       NC       NC
79       Vcc       NC
80       NC       Vcc
81       NC       Vcc
82       GND       GND
83       NC       NC  (May be Vpp on programmable modules)
84       D0 L       D0 LL
85       D1 L       D1 LL
86       D2 L       D2 LL
87       D3 L       D3 LL
88       Vcc       NC
89       NC       Vcc
90       Vcc       NC
91       D4 L       D4 LL
92       D5 L       D5 LL
93       D6 L       D6 LL
94       D7 L       D7 LL
95       GND       GND
96       D8 L       D8 LL
97       D9 L       D9 LL
98       D10 L       D10 LL
99       D11 L       D11 LL
100       Vcc       NC
101       NC       Vcc
102       NC       NC
103       D12 L       D12 LL
104       D13 L       D13 LL
105       D14 L       D14 LL
106       D15 L       D15 LL
107       GND       GND
108       A0       A0
109       A1       A1
110       NC       NC
111       A3       A3
112       A5       A5
113       A7       A7
114       A9       A9
115       _CE       _CE
116       Vcc       1Kohm to GND?
117       NC OR WE for back of module on programmable modules, may also connect to 37
118       _OE L       _OE all, also connects to 38
119       NC       NC
120       Vcc       NC
121       NC       Vcc
122       NC       NC
123       GND       GND
124       A11       A11
125       A13       A13
126       A15       A15
127       A17       A17
128       NC       NC
129       NC       NC
130       NC       NC
131       NC       NC
132       NC       NC
133       GND       GND
134       D0 H       D0 LH
135       D1 H       D1 LH
136       D2 H       D2 LH
137       D3 H       D3 LH
138       Vcc       NC
139       NC       Vcc
140       NC       NC
141       D4 H       D4 LH
142       D5 H       D5 LH
143       D6 H       D6 LH
144       D7 H       D7 LH
145       GND       GND
146       D8 H       D8 LH
147       D9 H       D9 LH
148       D10 H       D10 LH
149       D11 H       D11 LH
150       Vcc       NC
151       NC       Vcc
152       NC       NC
153       D12 H       D12 LH
154       D13 H       D13 LH
155       D14 H       D14 LH
156       D15 H       D15 LH
157       GND       GND
158       NC       NC
159       Vcc       NC
160       NC       Vcc 

Notes:

1) CE (pin 115) can simply be tied low or not. 2) OE low (pin 118) and OE high (pin 38) do not need to be connected together on the firmware module--they're connected on the motherboard. 3) Pin 116 connects to the CE_ of the motherboard ROM on PS and 7200 machines. If you tie it high, it disables the motherboard ROM so that the module ROM/firmware can take over. 4) While pin 122 may be grounded on some Beige modules, connecting it to ground seems to disable support for more than 512 MB of RAM in the Beige. 5) The Beige will not work with 120 ns flash. 90 ns or faster is needed, although I haven't tested 100 ns. 6) The PowerSurge seems to work with 120 ns flash, but stick to 90 ns or better to be safe.