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SIMM
Prior
generations, when CPU processed in 8 bits or 32 data bits (which is
1Byte or 4 Bytes), there were Single In-Line Memory Module (SIMM) in 30
and 72 pin configuration modules to support 8 data bit or 32 data bit
CPUs, respectively. With SIMMs, memory chips are soldered onto a modular
printed circuit board (PCB), which inserts into a socket on the system
board. As shown in the graph, the golden parts are the pins and there
are 72 pins in this type. Some refer to these golden parts as "Golden
fingers".
Graph 1. 72
pin SIMM.
Graph 2. 72
pin SIMM.
DIMM
Dual
In-line Memory Modules (DIMM) closely resemble SIMMs. The difference
between SIMM and DIMM is on a SIMM, pins on opposite sides of the board
are "tied together" to form one electrical contact; on a DIMM, opposing
pins remain electrically isolated to form two separate contacts.
DIMM are
often used in computer configuration that support a 64-bit memory bus.
SDRAM are more soldered onto a 168-pin PCB to transfer 64 bits of data
at a time. But DDR tendes to be soldered onto a 184-pin PCB
Graph 3.
168-pin DIMM. (SDRAM). Both sides have 84 golden fingers.
Graph 4.
184-pin DIMM. (DDR). One side has 92 pins.
So-DIMM
Small
Outline Dual In-line Memory Modules ( SO- DIMM) used in notebook
computers requires significantly smaller sides than the standard DIMM.
Graph 5.
144-pin SO-DIMM. (SDRAM).
Graph 6.
200-pin SO-DIMM. (DDR).
RI-DIMM and SO-RIMM
RIMM is the
trademarked name for a Direct Rambus memory module. RIMMs look similiar
to DIMMs, but transfer data in 16-bit batches. The faster access and
transfer speed generates more heat, therefore RIMM usually covers a heat
spreader (made by aluminum sheath) to protect the chips from
overheating.
Graph 7.
184-pin RIMM.
This is why
different types and number of pins need different sockets which are not
substitutable.
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