Ram
RAM, short for Random Access Memory
is the short storage area for your PC. Often just called memory or system memory
RAM is just an electromagnetic storage that loses all its data once the power
has been removed. RAM is used by your operating system and other programs and
games in order to store data that is required at speed. Computers with large
amount of memory often perform faster simply because the CPU is not idle waiting
for data to be retrieved from slower components such as the hard drive and can
be stored in memory.
Why is RAM considered Random
Access
 RAM can be
accessed by the computer for any piece of data in any cell of the memory bank.
There is no need to go through the entire memory bank to get to the data you
require. The opposite to Random access is serial access. SAM or Serial Access
Memory needs to be read from the start to get to the data you require. An
example of SAM storage would be a cassette tape. Of course there are things
which fit in-between these two examples such as a CD or DVD. Because these have
tracks they can be random access to a point but then need Serial access to get
to the exact spot required.
How does RAM store data
RAM consists of many capacitors and
transistors. A capacitor and a transistor are paired together to make a memory
cell. The capacitor represents one "bit" of data, the transistor is able to
change the state of the capacitor to either a 0 or a 1. the Zero's and ones when
read in a sequence represent the code which the computer understands. This is
called binary data because there is only two states that the capacitor can be
in.
In order for a capacitor to achieve
a value of 1 it needs to be filled with electrons. To achieve a value of 0 the
capacitor needs to be emptied of electrons. You may of noticed when purchasing
RAM that many types of RAM you buy are called DRAM or SDRAM. DRAM or Dynamic
Random Access Memory has a small problem with the capacitors holding a value of
1. It is called dynamic RAM because its state of 1 or 0 needs to be constantly
refreshed on order to stay in the correct state. In order to demonstrate this
and for a much more detailed look into the workings of RAM a good site site is
How stuff works. This article will show you a much more technical look at the
workings of RAM and has a great Diagram to illustrate the nature of Dynamic
Random Access Memory
There is a type of RAM that doesn't
have to be refreshed constantly. This is called SRAM or Static RAM. Static RAM
uses a type of Flip Flop to hold the data in the cell. This can take around 6
transistors on a chip per cell rather than just the one., The consequences are
that Static RAM needs more chips per Mb than DRAM and therefore is much more
expensive.
Types of RAM
Down the years the face of RAM has
changed dramatically in the early days of computing we had the SIMM. SIMM was a
Single Inline Memory Module. Moving on the next logical step was the DIMM,
Double Inline Memory Module. The introduction of DIMM's brought with it new
speeds and sizes to give computers more power than ever before. The big advances
in recent years has been the introduction of DDR RAM (Double Data Rate). DDR
effectively doubled the speed that RAM could transfer data without actually
increasing the MHz. E.g. a stick of PC133 (133MHz) RAM with DDR would
effectively transmit data at 266MHz but still have a bus speed of 133Mhz.
The other big memory type of the
recent past is RAMBUS memory. Rambus memory uses a memory module called a RIMM (RAMBUS
Inline Memory Module) RIMM's are specials high speed memory chips working upto
800Mhz. They require special motherboard support and are priced higher than that
of standard memory modules.
Measuring the Speed of RAM
Like CPU's RAM is measured in MHz.
The higher the MHz the greater the speed of the RAM. To keep this calculation
simple when dealing with DDR RAM, retails often simply put the effective MHz
rating. For example a 133Mhz DDR module would be advertised as 266Mhz. That is
basic speed test of the memory module. However there is another important factor
in high performance memory and that is CAS latency.
BY-http://www.pantherproducts.co.uk
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