The Dell OptiPlex 3040 Micro still uses DDR3L — two slots, no expansion surprises

Two slots, low-voltage DDR3 SO-DIMMs. The 3040 predates the DDR4 transition in Dell’s Micro lineup, so you’re shopping for DDR3L — which is still cheap but increasingly hard to find in larger capacities. Two slots means dual-channel is on the table, but max capacity isn’t listed, so check Dell’s spec sheet before buying modules.