47Upgrading the system memoryAcer Altos R5250 server supports sixteen DDR2 DIMM slots. The DIMMslots support dual channel DDR2-667 registered ECC memory modules.Important:When you are using a single-processor server, you should install apair of identical modules into the DIMM A1 and B1, DIMM A2 andB2, DIMM A3 and B3, or DIMM A4 and B4 slots.The DIMM C1 to DIMM D4 slots are enabled when a secondprocessor is installed on the mainboard. For instructions on how toinstall a second processor, see “To install a second processor”section on page 46.When you are using a dual-processor server, you should employ apaired DIMM configuration by installing modules in the DIMM A,B and DIMM C, D slots.Memory module population guidelines• Memory modules must be installed or removed in matched pairs,following the slot sequence listed below.• CPU 1 — Populate DIMM slots A1 and B1 first, followed byslots A2 and B2, A3 and B3, and A4 and B4• CPU 2 — Populate DIMM slots C1 and D1 first, followed byslots C2 and D2, C3 and D3, and C4 and D4Note: Refer to “Mainboard layout” on page 11 for the location ofthe DIMM slots for each processor.3344DIMMC4DIMMD4DIMMC3DIMMD3DIMMC2DIMMD2DIMMC1DIMMD1CPU2CPU1
