Owner's Manual
Page 64
Otherwise, your computer during a memory upgrade, keep them separate from any new module(s) that you may have, even if you purchased the new module(s) from Dell. The recommended memory configurations are: matched memory modules installed in DIMM connectors 1 and 2 and another matched memory modules installed in DIMM connectors 3 and 4. Recommended memory ...
Otherwise, your computer during a memory upgrade, keep them separate from any new module(s) that you may have, even if you purchased the new module(s) from Dell. The recommended memory configurations are: matched memory modules installed in DIMM connectors 1 and 2 and another matched memory modules installed in DIMM connectors 3 and 4. Recommended memory ...