RAM memory (Random Access Memory) is your computer’s short-term memory. Anything you’re currently working on is held in your computer’s RAM for easy access and modification. When you’re finished working on something and save your document, your computer moves the information from the RAM to the hard drive, your computer’s long-term memory. The problem with RAM is anything in it disappears when power is shut off, leaving it a faster but less safe means of storing information. Computers have the ability to use a portion of the hard drive as ‘virtual memory’, storing less-used information temporarily on the hard drive to free up the actual RAM memory for tasks that are being worked on. However, when the information in virtual memory on the hard drive needs to be accessed, this creates a delay as the slower hard drive loads information into the RAM. Therefore, it helps your system’s speed and operating to have more RAM available for programs and tasks.
How much RAM memory is enough? It depends a lot on what operating system you run and what you plan to do with the computer. A computer running Windows 98 can be fine with 256MB or 512MB of RAM, because the operating system and the programs that run on it are less complex. However a Windows XP computer is less functional with 512MB of RAM and really needs a gigabyte of memory for smooth operation. Windows Vista computer recommends having 1GB of memory to access the higher-end functions, but if you’re doing anything memory intensive with a Windows Vista computer, such as gaming or PhotoShop, 1.5GB or even 2GB or more of memory is a good idea.
Fast Page Mode (FPM) RAM memory is an earlier type of RAM that attempts to provide greater efficiency by keeping the same unit of RAM open while repeatedly reading and writing to it, thus saving time by not requiring the RAM to repeatedly prepare to access the same unit of RAM. Since FPM is an older type of memory and not currently in use due to advancements in RAM technology, it’s fairly uncommon and comes only in smaller amounts of RAM. You can find FPM RAM available in sizes ranging from 8MB to 128MB.
EDO, or Extended Data Out memory is also an older type of RAM memory. Designed as an enhancement on FPM RAM, Extended Data Out holds open the data transfer portion of the RAM cycle from one cell until another cell is selected for output. The difference between EDO and FPM memory is that with EDO memory, a new cell can be accessed while the old one is still active. Like Fast Page Mode RAM, EDO memory is an older type not used in current systems, but is still available in sizes ranging from 8MB to 128MB.
Synchronous Dynamic Random Access Memory, or SDRAM, evolved out of the FPM and EDO standards. Unlike the previous types of RAM memory, which operate out of sequence with the rest of the system in an attempt to allow them to react as quickly as possible to memory commands, SDRAM operates with a clock cycle that regulates its operation so that it sends and receives data at the same time that the processor sends and receives information. Unlike previous memory types, SDRAM can accept and queue instructions in the pipeline, and perform them immediately as soon as the last command has completed. This type of RAM memory is the first type of memory that is still somewhat in use, though it is superseded by the DDR and DDR2 standards. SDRAM comes in a number of speeds, but the most common are PC66, PC100 and PC133, which correspond bus speeds of 66MHz, 100MHz and 133Mhz. This type of memory comes in sizes ranging from 32MB all the way up to 1GB modules.
Rambus RAM memory was developed as a possible successor to SDRAM. It operates at much faster speeds then SDRAM does, but operates through a narrow bus. In essence it sends data more quickly through the information pipe, but has a narrow pipe to send data through. Although Rambus was initially faster, its high production costs also translated to high cost for the consumer. What prevented Rambus from becoming the successor to SDRAM was the development of DDR RAM memory, which quickly grew to provide the same performance for a lower price to the consumer. Rambus is still in use today on a small number of motherboard types, and their modules come in sizes ranging from 64MB to 512MB.
DDR or Double Data Rate memory became the replacement for SDRAM and until recently has been the standard memory in the computer industry until the development of DDR2 memory, which has since begun replacing it. DDR RAM memory achieves faster results then SDRAM by sending data twice during a clock cycle, at the rising and the falling of the clock signal. This effectively doubles the bandwidth of DDR memory without increasing the speed of the memory used. DDR RAM is widely available, and comes in speeds ranging from 266MHz, 333MHz and 400MHz. Memory also varies in size from 128MB to up to 2GB in a single module.
DDR2 memory is the current standard, and is a direct extension of the DDR memory. Like its predecessor, DDR2 memory sends data on the rising and falling of the memory clock cycle, but sets the data bus to twice the speed of the memory, allowing the memory to send more information in the same time period. DDR2 memory initially had higher internal latencies then DDR memory, resulting in DDR and DDR2 RAM memory of the same speed performing equally, but DDR2 memory has since lowered the internal latencies and operates faster then DDR memory. Because it is the current market standard, DDR2 memory is easy to find, and comes in sizes ranging from 256MB all the way up to 4GB of memory.
If you’d like to know about the different sizes and formats of computer memory, take a look at the links on the sidebar, where you can see the different physical formats of memory available. If you’re interested in what type of memory your computer uses, click the ‘Check Your Computer’ link below, or enter your system’s model number to find out what type of RAM memory it uses, how much RAM it can use, and what some of the best memory upgrades for your system might be.