PC Hardware

RAM Packaging

Over the years, the way memory has been packaged and placed on the motherboard has changed several times. Early versions of RAM were installed as single chips, usually 1-bit wide dual inline package (DIP), as shown in Figure 7.1. In some cases, this was soldered right onto the motherboard, but most often it was seated in a socket, offering a simpler method of removal and replacement. Some older machines have special memory expansion cards that contain several rows of sockets. These cards are placed in a slot on the motherboard.

To upgrade or add memory, new chips had to be individually installed on the motherboard (eight or nine chips per row-nine chips if using parity). This could be challenging, because each chip has 16 wires that need to be perfectly aligned before insertion into the base. The notch in one end denotes the side that has pin 1.

Figure 7.1 A DIP DRAM Chip

As the amount of memory and the need for speed increased, manufacturers started to market modules containing several chips that allowed for easier installation and larger capacity. These modules come in a variety of physical configurations. Technicians must be able to identify both the type and amount of memory a computer requires for optimum performance.

The latter is very easy if the PC is operational: simply boot the system and note the memory values given during the POST. In some cases, this is also a useful way to determine if a memory block is improperly installed. If that is the case, the computer might fail to boot or the POST might report a lower figure than the actual amount of RAM present.