This should get it started. (courtesy of various mfg sites. i.e Crucial, Kingston)
FRONT SIDE BUS
The front side bus (FSB) is the main highway for data in your PC. It connects the processor,
chipset, DRAM, and graphics controller. FSB is described in terms of its width in bits and
its speed in MHz.
REFRESH RATE
In order to store data, DRAM needs a constant supply of electricity. "Refresh" is the process
of re-charging the individual cells in a DRAM chip, and the "refresh rate" is the number of
rows (in thousands) that are refreshed at once. Common refresh rates are 1K, 2K, 4K, and 8K.
DDR SDRAM and SDRAM
DDR SDRAM is a straightforward evolution from current single data rate (SDR) SDRAM. DDR, which
stands for Double Data Rate SDRAM, actually doubles the bandwidth available to your system and
runs twice as fast as regular SDRAM. For example, 266MHz DDR SDRAM (133MHz doubled) has the
bandwidth of 2.1GB/sec and is referred to as PC2100.
The big difference between DDR SDRAM and standard SDRAM is that DDR reads data on both the rising
and falling edges of the clock signal. Standard SDRAM, or single data rate (SDR) SDRAM, only
carries information on the rising edge of a signal. Basically this allows the DDR module to transfer
data twice as fast as SDR SDRAM. For example, instead of a data rate of 133MHz, DDR memory transfers
data at 266MHz.
RAMBUS DRAM
Rambus memory (RDRAM®) is a revolutionary step from SDRAM. It's a new memory design with changes to
the bus structure and how signals are carried. Rambus memory sends less information on the data bus
(which is 18 bits wide as opposed to the standard 32 or 64 bits) but it sends data more frequently.
It also reads data on both the rising and falling edges of the clock signal, as DDR does. As a result,
Rambus memory is able to achieve effective data transfer speeds of 800MHz and higher.
Another difference with Rambus memory is that all memory slots in the motherboard must be populated.
Even if all the memory is contained in a single module, the "unused" sockets must be populated with
a PCB, known as a continuity module, to complete the circuit.
Rambus DRAM modules are known as RIMM? modules (Rambus inline memory modules). Rambus memory supports
both ECC and non-ECC applications.
DDR Memory
PC1600 memory is DDR designed for use in systems with a 100MHz (effectively 200MHz in DDR mode)
front-side bus. The "1600" refers to the module's bandwidth (the amount of data it can move each
second), which is 1.6GB per second. PC1600 has essentially been replaced by PC2100, which is
backward compatible.
PC2100 DDR is designed for use in systems and motherboards which require a 133MHz front-side bus.
While the system or motherboard may operate a 133MHz front-side bus, its effective front-side bus
speed is 266MHz in DDR operation. To get the effective front-side bus speed of a DDR system, double
the operating frequency which in this case is 133 MHz to get the 266MHz.
PC2700 DDR is designed for use in systems and motherboards which require a 166MHz front-side bus,
with an effective front-side bus speed of 333MHz.
PC3200 DDR is designed for use in systems and motherboards which require a 200MHz front-side bus,
with an effective front-side bus speed of 400MHz.
DUAL BANKING
Dual banking is a way of designing a motherboard to improve the performance of a system by utilizing
two separate memory controllers. This allows two separate memory modules to be accessed at the same
time. The modules used in a dual-banked system are not special "dual-banked modules." Any like pair
of memory modules can be used in this way.
CL2 and CL2.5 DDR
CAS latency 2 parts process data a little quicker than CAS latency 2.5 parts in that you have to wait
a half clock cycle less for the initial data. However, after the first piece of data is processed, the
rest of the data is processed at equal speeds. Latency only affects the initial burst of data. Once data
starts flowing, there is no effect.
Bear in mind, a clock cycle for a system properly using a PC2100 DDR module is 8 nanoseconds, so the
difference between CAS latency 2 and CAS latency 2.5 for PC2100 parts is 4 billionths of a second. You
probably won't be able to notice the difference.
Memory Module Identification
184-pin DIMM approx. 5.375" x 1" (13.65cm x 2.54cm): used to provide DDR SDRAM memory for desktop computers
168-pin DIMM approx. 5.375" x 1" (13.65cm x 2.54cm): commonly found in Pentium and Athlon systems
144-pin MICRODIMM approx. 1.545" x 1" (3.92cm x 2.54cm): are commonly found in sub-notebook computers
100-pin DIMM approx. 3.5" x 1.25" (8.89cm x 3.175cm): are commonly found in printers
200-pin SODIMM approx. 2.625" x 1" (6.67cm x 2.54cm): are commonly found in laptop computers
144-pin SODIMM approx. 2.625" x 1" (6.67cm cm x 2.54cm): are commonly found in laptop computers
72-pin SODIMM approx. 2.375" x 1" (6.03cm x 2.54cm): are commonly found in laptop computers
72-pin SIMM approx. 4.25" x 1" (10.8cm x 2.54cm): found in older desktop computers, such as the 486 and early Pentium models
30-pin SIMM approx. 3.5" x .75" (8.89cm x 1.91cm): found in older desktop computers, such as the 386 and 486 models.
All 30-pin SIMMs use FPM memory technology
