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Caution:
Please read our safety
information before attempting any testing or repairs.
The memory chips store information temporarily, for short term use. A PC's memory only contains information while the PC is on. When the PC is turned off, the information in the memory chips disappears. In some ways, the information in memory is similar to a thought you are having, it disappears when you start thinking about something else.
A PC's memory is an entirely different thing from the hard disk "memory". The hard disk stores information "permanently" for long term use. Hard disk "memory" (more accurately called storage) is like writing down information and storing it in a filing cabinet.
Memory chips are mounted in groups onto a memory module. The total of all the chips combined on that module is the memory capacity. Memory modules can be combined in a PC to increase the total memory capacity of the PC
Memory capacity is measured in
megabytes (MB) or gigabytes (GB). In memory that predates SDRAM
the speed was measured in nanoseconds (NS) and which measures
the time it takes to access memory. Beginning with SDRAM the
speed is the measurement of clock cycles and are measured in
megahertz (MHz).
There are several types of memory,
including FPM, EDO, SDRAM, RDRAM and DDR SDRAM. FPM, Fast Page
Mode and EDO, Extended Data Output are extinct. Synchronized
Dynamic Random Access Memory (SDRAM) is still
available, but it isn't used in newer systems. Most PCs
built in the past 2 years use DDR SDRAM. It uses a technology
called "Double Data
Rate" and so is
known as DDR. DDR memory is available in three flavors
DDR, DDR2 and the latest, DDR3. Each is incompatible with the
other.
The size and shape of a memory module is called "form factor" and usually is either a SIMM or a DIMM (Single or Double In-line Memory Module). SIMMs come in 30 pin or 72 pin modules and DIMMs come in 168 pin modules.
The current minimum standard for
memory in new PCs is 512MB and many PCs include 1GB. As the
price for memory continues to drop, larger memory modules become
more practical. If your PC has less than 512MB of RAM, and
is able to support more, it is a virtual certainty that your
PC performance would receive a boost from the addition of more
memory. |
