Computer Memory Guide - What you need to know
about purchasing computer memory.
Computer memory, also known as RAM (random access memory) is the place in the
computer where the operating system stores information about applications and
data in current use so that they can be quickly reached by the computers
RAM is much faster to read from and write to than the other kinds of storage
in a computer, the hard disk, floppy disk, and CD-ROM. However, the data in RAM
only stays there only as long as your computer is running. When you turn the
computer off, RAM loses its data. When you turn your computer on again, your
operating system and other files are once again loaded into RAM, usually from
your hard disk. There is technology in the works to fix this problem, but that
will take a while to reach the rest of us.
Computer memory can be compared to a persons short-term memory, and the hard
disk to the long-term memory. The short-term memory focuses on work at hand, but
can only keep so many facts in view at one time. Long term memory is much more
abundant, and lasts much longer.
Computers work much like this as well, RAM takes care of the current
workload, and the hard drive stores long term data. The faster these two can
work, the faster your computer can calculate.
There are three types of computer memory.
SDRAM – The slowest, yet cheapest
DDR – Fast and efficient, and very cost effective
DDR2 - The fastest available memory to date
RDRAM – Use to be the fastest and the most expensive, generally a pain since
they have to be used in pairs
The Motherboard must be compatible with the type of memory you want to use.
Several Motherboard companies produce Motherboards with SDRAM and DDR slots,
which can NOT be used at the same time, but it is nice to have a choice of what
you can use.
Each type of RAM also has various speeds at which it works, and the
Motherboard must also support these speeds. DDR for example currently comes in
either pc2100 , pc2700, & pc3200, while DDR2 comes in pc3200, pc4200, pc5400,
pc6400, & pc8000.
RAM also works at various megahertz, limited by the megahertz that the Front
Side Bus on your motherboard works (the Front Side Bus, or FSB, is the channel
on the motherboard used to transfer information from the CPU to the RAM) so if
you have RAM that works at 500 megahertz, and the FSB of your motherboard only
runs at 333 megahertz, then 333 megahertz is the fastest your memory can run as
One very important note about computer memory, is you do not want to mix
various speeds of memory, because the Motherboard will take the slowest speed
and dummy all the rest of the fast memory to that slower speed. Here’s an
You have three sticks of DDR computer memory in your computer, 2 pc2700’s,
and 1 pc2100. The Motherboard slows down the 2 pc2700’s to be the speed of the
pc2100, so that they’re all working at the same speed.
While this scenario works ok, it is not a good idea, because you have lost
the value of the higher speed RAM.
Donny Duncan, the author of Computer
Discounts Guide has been in the computer field for over thirteen years.