Owner's Manual (PDF)
Page 28
... possible, do not pair an original memory module with a new memory module. Otherwise, your computer may have, even if you purchased the new module(s) from Dell. CAUTION: If you remove the original memory module(s) from your computer may not boot. Recommended memory configuration: Type Slots 1600 MHz DDR3 Slots 1 and 2 or... slots 1 through 4 28 Memory Module(s) Replacing Memory Module(s) CAUTION: If the memory module is not installed correctly, your computer during a memory upgrade, keep them separate from any new module(s) that you may not start properly.
... possible, do not pair an original memory module with a new memory module. Otherwise, your computer may have, even if you purchased the new module(s) from Dell. CAUTION: If you remove the original memory module(s) from your computer may not boot. Recommended memory configuration: Type Slots 1600 MHz DDR3 Slots 1 and 2 or... slots 1 through 4 28 Memory Module(s) Replacing Memory Module(s) CAUTION: If the memory module is not installed correctly, your computer during a memory upgrade, keep them separate from any new module(s) that you may not start properly.