SIMM details |
32MB 70ns Parity Gold SIMM (Single Inline Memory Module) 24-Chip shown.
Jumper Description
Jumper 0 | Pin 76 | In this example not present | |
R1 | Jumper 1 | Pin 67 | In this example not set |
R2 | Jumper 2 | Pin 68 | In this example set |
R3 | Jumper 3 | Pin 69 | In this example set |
R4 | Jumper 4 | Pin 70 | In this example not set |
Jumper 5 | Pin 71 | In this example not present | |
Ground | Pin 72 |
Most modules do not explicitely have all 6 jumpers marked since the jumpers 0 & 5 are normally open and 3 & 4 are never set on a 60ns module, one can save a couple pennies by omitting them...
The capacitors C3, C4 are decoupling condensators for higher frequencies. C25 is a filter condensator for lower frequencies. On other modules you may find different numberings and/or locations and/or counts of the capacitors.
In addition to this you will commonly find a decoupling capacitor for each DRAM-Chip, either under or next to the chip.
SIMM Jumper Settings
60 ns | 70 ns | 80 ns | Comment | |
4 Mb | 12.. | 123. | 12.4 | |
8 Mb | .... | ..3. | ...4 | |
16 Mb | 1... | 1.3. | 1..4 | |
32 Mb | .2.. | .23. | .2.4 | 32MB 70ns Parity SIMM shown above |
A Number in a field represents the Jumper (0 Ohm SMD Resistor) set
i.e. this pin is connected to ground (pin 72).
Likewise a . represents a open connection.
Some systems check for the actual SIMM speed installed. I.e. Installing a faster SIMM than specified may not work even though technically it would.