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RAM is the best known form of computer memory and easy to upgrade. See more computer hardware pictures.
Random access memory (RAM) is the best known form of computer memory. RAM is considered "random access" because you can access any memory cell directly if you know the row and column that intersect at that cell.
The opposite of RAM is serial access memory (SAM). SAM stores data as a series of memory cells that can only be accessed sequentially (like a cassette tape).
If the data is not in the current location, each memory cell is checked
until the needed data is found. SAM works very well for memory buffers, where the data is normally stored in the order in which it will be used (a good example is the texture buffer memory on a video card). RAM data, on the other hand, can be accessed in any order.
Similar to a microprocessor, a memory chip is an integrated circuit (IC) made of millions of transistors and capacitors. In the most common form of computer memory, dynamic random access memory (DRAM), a transistor and a capacitor are paired to create a memory cell, which represents a single bit of data. The capacitor holds the bit of information -- a 0 or a 1 (see How Bits and Bytes Work
for information on bits). The transistor acts as a switch that lets the
control circuitry on the memory chip read the capacitor or change its
state.
Power Up with RAM |
A capacitor is like a small bucket that is able to store
electrons. To store a 1 in the memory cell, the bu
cket is filled with
electrons. To store a 0, it is emptied. The problem with the
capacitor's bucket is that it has a leak. In a matter of a few
milliseconds a full bucket becomes empty. Therefore, for dynamic memory
to work, either the CPU or the memory controller
has to come along and recharge all of the capacitors holding a 1 before
they discharge. To do this, the memory controller reads the memory and
then writes it right back. This refresh operation happens automatically
thousands of times per second.
The capacitor in a dynamic RAM memory cell is like a leaky bucket.
It needs to be refreshed periodically or it will discharge to 0.
This refresh operation is where dynamic RAM gets its name.
Dynamic RAM has to be dynamically refreshed all of the time or it
forgets what it is holding. The downside of all of this refreshing is
that it takes time and slows down the memory.
In this article, you'll learn all about what RAM is, what kind you should buy and how to install it. See the next page to learn more about dynamic RAM and memory cells.
