SIMM details

72 pin SIMM

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.