Type

Type

• FPM – Fast Page - If you have a 486, you probably have FPM

• EDO – Extended Data Out - If you have an early Pentium system, you probably have EDO

• SDRAM - If you have a Pentium or Celeron system purchased in 1999, you probably have SDRAM

Sockets

Memory modules plug into a socket on the motherboard. There are three socket types.

• SIMM – 30 pin – 3 inches in length

• SIMM – 72 pin – 4 inches in length

• DIMM – 168 pin – 5 inches in length

Most older 486 machines will use 30 pin modules. Later model 486 and Pentium machines will probably use 72 pin modules. More recent Pentium machines may have 168 pin.

Amount

Memory sizes increase by the power of 2. This results in sizes of 1, 2, 4, 8, 16, 32, 64, 128, 256 MBs.

• On some older 486 machines, one memory module can be added at a time.

• On most Pentium machines, modules must be added in pairs.

• Each pair must be of the same size.

• SDRAM modules can be added one at a time.

For example, if you have 8 MBs of memory on a Pentium, you have two 4 MB modules. To increase to 16 MBs, you need to add two more 4 MB modules. To increase to 24 MBs, you need to add two 8 MB modules.

30 pin modules

For 30 pin modules you will see something like

• 1 x 9-60

• 4 x 9-70

• 4 x 8-70

The first number is the size in MB’s. In our example this would be 1MB or 4MB.

The second number represents parity. The value 9 represents parity and 8 represents non-parity. (Of course that makes a lot of sense!) The 9 or 8 also identifies that it is a 30 pin module.

The third value represents the speed.

72 pin modules

For 72 pin modules you will see something like

• 1 x 32-60

• 2 x 32-70

• 4 x 36-60

• 8 x 36-70

Just like the 30 pin modules, the first value represents the size, EXCEPT it only represents ¼ of the total memory size. Don’t ask why, just accept it. So the value of 4 represents a 16 MB (4 x 4) module. A value of 8 represents a 32 MB (4 x 8) module.

The second value, again just like the 30 pin, represents parity and the number of pins. 36 is used for parity and 32 for non-parity. You aren’t asking why again, are you?

The third value represents the speed, the same as the 30 pin.