IBM 71413SU Technical Reference - Page 23

Release latch The x3850 M2 and x3950 M2 support up to 4 memory cards, and each card holds up to 8 DIMMs. Each memory card has 8 DIMM sockets. DIMMs must be installed in matched pairs. Either 4 or 8 DIMMs are installed in pairs across either 2 or 4 memory cards as standard. Figure 12 x3850 M2 and x3950 M2 memory card and location Note the following key configuration rules: Because the x3850 M2 and x3950 M2 use two-way interleaving memory, DIMMs must be installed in matched pairs. Memory cards have part number 44E4252. Two or four are standard in the x3850 M2 and x3950 M2 (depending on the model; see "Current models" on page 12 or Table 3 on page 12 for more information), and up to a maximum of four can be installed. Each memory card has eight DIMM sockets. There are two ways to fill the DIMMs sockets, depending on whether cost or performance is the more important consideration: - Cost-effective configuration To minimize cost, you can install the memory DIMMs by filling each memory card before adding DIMMs to the next memory card. - Performance-optimized configuration As described in "IBM XA-64e fourth-generation chipset" on page 14, there are eight independent memory ports. Therefore, to optimize performance, you need to install four memory cards and then spread the DIMMs, still installed in matched pairs, across all four memory cards before filling each card with two more DIMMs. A more detailed description and the exact sequence for installation is provided in System x3850 M2 Installation Guide. If you want to install the full 256 GB, you will need to remove the existing DIMMs and fully populate the x3850 M2 and x3950 M2 with four memory cards, each with eight 8 GB DIMMs. IBM System x3950 M2 and x3850 M2 Technical Introduction 23