COMPUTER MEMORY TYPE

Desktop RAM

Desktop personal computers require Non-ECC Unbuffered RAM. There can be exceptions, so use the information below to determine what memory type your machine is currently running.

Non-ECC unbuffered memory usually has 8 chips per side and can be single sided or double sided. Low density dual channel desktop RAM commonly has 8 chips on both sides.

Please note that server RAM does not work in most desktop computers. Server RAM is ECC Registered, and desktop RAM usually needs to be Non-ECC and Non-Registered (unbuffered).

Desktop SDRAM - 168 pins, 2 notches at the bottom (PC100 or PC133)

Desktop DDR - 184 pins, 1 notch at the bottom (PC2100, PC2700 or PC3200).

Desktop DDR2 - 240 pins, 1 notch at the bottom. 

(Note-The notch in DDR2 RAM is in a slightly different location to prevent it from being installed in machines that require DDR RAM. DDR2 is not backwards compatible with DDR1.)

Desktop DDR-3 - 240 pins, 1 notch at the bottom. 

(Note-The notch in DDR3 RAM is in a different location to prevent it from being installed in machines that require DDR or DDR2 RAM. DDR3 is not backwards compatible with DDR2.)

Laptop RAM

Laptop computers require Non-ECC Unbuffered SODIMMs. The module size is physically about half as long as desktop memory.

Laptop SDRAM - 144 pins (PC100 or PC133).

Laptop DDR (DDR1) - 200 pins (PC2100, PC2700 or PC3200).

Laptop DDR2 - 200 pins 

(Note-The notch is in a slightly different position to prevent DDR2 RAM from being installed in DDR1 laptops. DDR2 is not backwards compatible with DDR1.)

Laptop DDR3 - 204 pins
(Note-DDR3 is not backwards compatible with DDR2 or DDR1.)

NOTE--A RAM Timeline

1997 (SDRAM) PC66 SDRAM 66MHz
1999 (RDRAM) RDRAM 800MHz
2000 (DDR-SDRAM) DDR SDRAM 266MHz
2004 (DDR2-SDRAM) DDR2 SDRAM 533MHz
2007 (DDR3-SDRAM) DDR3 SDRAM 1066 - 1333MHz