RAM

[Violent Unrest in Allentown]

As I increase my knowledge of computers, I have found a certain topic escapes my understanding at times.

I feel like I know the purpose of RAM, but the varities confuse me. When I play around at crucial, you have to give the make and model of your computer so they can sell you the right kind of RAM. Why, then, is there only one kind of ram on the shelves at Circuit City? Is this some kind of 'one-size-fits-all' RAM? If it is, how can I tell if RAM is multipurpose instead of specific? Are there disadvantages to this type of RAM?

[TemporalRift]

There is no multi purpouse RAM, just some varieties are more common than others. There are three basic varieties. SIMM's (Single In Line Memory Modules) used now only for some laptops. DIMM's (Dual In Line Memory Modules) used for newer laptops, and DDR, whose acryonym escapes me a the moment

It gets complicated with DDR, because there isn't just DDR memory, there are at least four different varieties of DDR memory all posessing the standard set of chip sizes (256 meg per chip, 512 per, 1024 per)

DDR however is the standard now, so this memory might be the only kind Circut City sells, and the distinction is written on the box, if it's DDR166, DDR266, DDR400, or DDR2. The first three only differ in bus access speed, while the last is direct chip access DDR only used for some video cards.

Buying the right variety of RAM is crucial, especially if you're adding to an existing set of RAM, since SIMM's and DIMM's need to be added in pairs, and DDR memory can only be added to a system using the same speed of DDR, you can't have a DDR266 stick and a DDR400 stick working together, if the board supports DDR400 it'll just shut off the 266 stick. Also, higher end processors won't even run at speed unless the RAM you're using is fast enough.

Moral. Buy DDR400 AKA PC3200 RAM if your motherboard supports it and nothing else