Understanding Computer Memory
SDRAM comes in a 168-pin dual inline memory module (DIMM) package. It comes in two
speeds, 100 MHz (PC100) and 133 MHz (PC133). It comes in 3.3 volt and 5.0 volt versions.
Some SDRAM contain extra circuitry called "error checking and correction" (ECC) that
stores extra bits along with the data. The extra bits are used to verify the integrity
of the data and correct any errors.
New systems use a type of memory that can access data on the rising edge and the
falling edge of the system clock pulses. This means your computer can access the data
in memory at double the rate, hence the term "Double Data Rate SDRAM (DDR-SDRAM).
DDR-SDRAM comes packaged in a 168-pin DIMM. It comes in two speeds, 266 MHz (PC2100)
and 333 MHz (PC2700). If your motherboard has more than one memory module slot, and you
have only one memory module, you might be required to install the single DIMM in slot 1.
Some Intel motherboards use Rambus DRAM (RDRAM). RDRAM uses a proprietary communications
channel to access memory. RAMBUS is packaged in a 184-pin RAMBUS In-line Memory Module
(RIMM). There are two connectors on an Intel Rambus motherboard, each must contain
either a RIMM or a C-RIMM. A C-RIMM (continuity RIMM) does not contain memory. It is a
module that provides a path pass-through for the signals.
If you have an older computer, its main memory may use "fast page memory" (FPM) or
"extended data output" (EDO) memory. Some of these used a special "parity bit" to
validate the integrity of the data. These older types of memory came packaged in a 30
pin single inline memory module (SIMM) or a 72 pin SIMM.
If you want to upgrade your computer's memory, make sure you are using the correct
type of memory for your motherboard. It's important to study the manual that came with
your motherboard to determine exactly what type and speed of memory is required.
More Computer Anatomy Articles:
• How is Data Written, Stored On, and Erased From Hard Disks?
• Building Your Own PC! - The Motherboard is the Core of the PC
• An Overview of the Printed Circuit Board (PCB) Fabrication Process
• IEEE-1394 FireWire
• Hard Disc Fundamentals
• Motherboard Basics
• CPU Sockets Roundup
• Understanding Computer Memory
• Installing an Optical Drive
• A Guide to Basic PC Cooling
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