Dell OptiPlex 755 User's Guide - Page 313

Memory You can increase your computer memory by installing memory modules on the system board. Your computer supports DDR2 memory. For additional information on the type of memory supported by your computer, see the appropriate specifications for your system in this book. DDR2 Memory Overview • When installed in pairs, DDR2 memory modules should be of matched memory size and speed. If the DDR2 memory modules are not installed in matched pairs, the computer will continue to operate, but with a slight reduction in performance. See the label on the upper-right or upper-left corner of the module to determine the module's capacity. NOTE: Always install DDR2 memory modules in the order indicated on the system board. The recommended memory configurations are: - A pair of matched memory modules installed in DIMM connectors 1 and 2 or - A pair of matched memory modules installed in DIMM connectors 1 and 2 and another matched pair installed in DIMM connectors 3 and 4 NOTICE: Do not install ECC memory modules. • If you install mixed pairs of PC2-5300 (DDR2 667-MHz) and PC2-6400 (DDR2 800-MHz) memory, the modules function at the speed of the slowest module installed. • Be sure to install a single memory module in DIMM connector 1, the connector closest to the processor, before you install modules in any other connector. Memory 313