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SIMM's
The term SIMM stands for Single In-Line Memory Module. With SIMMs,
memory chips are soldered onto a modular printed circuit board
(PCB), which inserts into a socket on the system board.
The first SIMMs transferred 8 bits of data at a time. Later, as
CPUs began to read data in 32-bit chunks, a wider SIMM was
developed, which could supply 32 bits of data at a time. The
easiest way to differentiate between these two different kinds of
SIMMs was by the number of pins, or connectors. The earlier
modules had 30 pins and the later modules had 72 pins. Thus, they
became commonly referred to as 30-pin SIMMs and 72-pin SIMMs.
Another important difference between 30-pin and 72-pin SIMMs is
that 72-pin SIMMs are 3/4 of an inch (about 1.9 centimeters)
longer than the 30-pin SIMMs and have a notch in the lower middle
of the PCB. SIMMs were popular in 386 and 486 machines.
64MB 72 pin EDO SIMM
DIMM's
Dual In-line Memory Modules, or DIMMs, closely resemble SIMMs and install vertically into
the expansion sockets.
The principal difference between the two is that 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.
168-pin DIMMs, also known as SDRAM, transfer 64 bits of data at a time and are typically
used in computer configurations that support a 64-bit or wider
memory bus. Some of the physical differences between 168-pin DIMMs
and 72-pin SIMMs include: the length of module, the number of
notches on the module, and the way the module installs in the
socket. Another difference is that many 72-pin SIMMs install at a
slight angle, whereas 168-pin DIMMs install straight into the
memory socket and remain completely vertical in relation to the
system motherboard. 168 Pin DIMMs were popular in the Pentium 1 PCs and on
socket 7 motherboards. Some newer motherboards like the socket A
Boards may also take 168 pin DIMMs but many are now going to the
newer 184 pin DIMM known as DDR SDRAM.
128MB PC133 164 pin SDRAM 133MHz
128MB PC2100 184 pin DDR 266Mhz RIMM's
RIMM's are a memory module developed by Kingston Technology Corp.
that takes up less space inside the computer than the older DIMM
module and has different PIN characteristics. A RIMM has a 184-pin
connector and an SO-RIMM module has a 160-pin connector. An SO-RIMM
is smaller and is used in systems that require smaller form
factors. While RIMM is commonly believed to stand for "Rambus
inline memory module," Kingston Technology has trademarked "RIMM"
and uses only that term this is why this form of memory is often
known as RAMBUS or RD-RAM. All memory slots of the motherboard
must be filled if not with memory, then with a special adaptor
known as a C-RIMM.
128MB PC800 184 pin RDRAM 800MHz OTHER COMMON MEMORY
TERMS EXTENDED DATA OUT (EDO)
EDO type memory became popular in the mid 90s it allowed
consecutive memory accesses to occur much faster. This meant the
memory controller could save time by cutting out a few steps in
the addressing process. EDO enabled the CPU to access memory 10 to
15% faster than standard memory. 72 pin EDO SIMMs cannot be used in conjunction with other types of
memory, i.e. you cant use 3 72 pin EDO SIMMs and one normal SIMM.
64MB 72 pin EDO SIMM
SYNCHRONOUS DRAM (SDRAM)
In late 1996, SDRAM began to appear in systems. Unlike previous
technologies, SDRAM is designed to synchronize itself with the
timing of the CPU. This enables the memory controller to know the
exact clock cycle when the requested data will be ready, so the
CPU no longer has to wait between memory accesses. SDRAM chips
also take advantage of interleaving and burst mode functions,
which make memory retrieval even faster. SDRAM modules come in
several different speeds so as to synchronize to the clock speeds
of the systems they'll be used in. For example, PC66 SDRAM runs at
66MHz, PC100 SDRAM runs at 100MHz and PC133 SDRAM runs at 133MHz. Faster SDRAM speeds such as 200MHz and 266MHz are currently
in development. 168 pin SDRAM is popular on the socket 370 celeron
/ pentium 3 and the socket A AMD motherboards.
128MB PC133 168 pin SDRAM 133MHz
DOUBLE DATA RATE SYNCHRONOUS DRAM (DDR SDRAM)
DDR SDRAM, is a next-generation SDRAM technology. It allows the
memory chip to perform transactions on both the rising and falling
edges of the clock cycle. For example, with DDR SDRAM, a 100 or
133MHz memory bus clock rate yields an effective data rate of
200MHz or 266MHz. 184 pin DDR SDRAM is popular on the new socket
478 Pentium 4 and socket A AMD Motherboards.
128MB PC2100 184 pin DDR 266Mhz
128MB PC2700 184 pin DDR 333MHz
DIRECT RAMBUS (RDRAM)
Direct Rambus is a new DRAM architecture and interface standard
that challenges traditional main memory designs. Direct Rambus
technology is extraordinarily fast compared to older memory
technologies. It transfers data at speeds up to 800MHz over a
narrow 16-bit bus called a Direct Rambus Channel. This high-speed
clock rate is possible due to a feature called "double clocked,"
which allows operations to occur on both the rising and falling
edges of the clock cycle. Also, each memory device on an RDRAM
module provides up to 1.6 gigabytes per second of bandwidth -
twice the bandwidth available with current 100MHz SDRAM. RDRAM
motherboards support the new Pentium 4 processor it is expected
that RDRAM will overtake DDR SDRAM as the popular choice for new
pentium's. RDRAM must be installed in pairs.
128MB PC800 184 pin RDRAM 800MHz |
