18.2. Installing Memory

The electrical traces from the memory chips are routed from the memory chips to gold pins located at the bottom of the memory module. The pins snap into slots on the motherboard or a memory board.

When single inline memory modules (SIMMs) are used, they must be installed in pairs. Dual inline memory modules (DIMMs) have memory chips on both sides, and each side has separate pins, for a total of 144 pins. Some DIMMs have 168 pins. The extra pins handle error checking and correcting (ECC) capabilities.

! Important

DIMMs with tin/lead pins must be used on system boards with tin/lead-plated contacts for the memory sockets. DIMMs with gold pins must be used on system boards with gold-plated contacts for the memory sockets. Mixing dissimilar-metal-contact DIMMs and their related sockets causes memory problems because of electrolysis-induced corrosion and damages the memory socket on the system board.

Memory must be added in banks of four DIMMs. Mixing of 50ns and 60ns memory is permitted; however, each bank of four DIMMs must contain the same size and speed DIMMs. Performance will default to the slower of the two speeds (that is, 60ns).

Installing memory modules with mismatching capacity (256MB, 512MB, and so forth) or configuration (single or double banked; buffered, registered, or unregistered) within the same multi-DIMM bank can result in errors. Problems such as boot failures, lockups, uncorrectable parity errors, or numerous correctable memory errors also can occur if the memory technology (EDO, PC100, PC133, and so forth) is not supported by the system in which the DIMMs are installed.

If memory errors occur, verify that the memory modules within each bank are matched in capacity, configuration, and technology. You can best accomplish this by matching the first eight digits of the nine-digit HP/Compaq part number. If they do not match, replace the memory modules with the correct spares kit.

At the next system Power-On Self-Test (POST), the server should report the new memory. The server will automatically incorporate the upgrade and start the operating system without any intervention. You might notice that the system executes more quickly.