The Dell OptiPlex 5000 SFF uses desktop UDIMMs, not laptop SO-DIMMs

The Dell OptiPlex 5000 SFF uses desktop UDIMMs, not laptop SO-DIMMs

This SFF variant takes full-size DDR4-3200 UDIMMs — not the laptop SO-DIMMs most mini PCs use. Two slots, 64 GB ceiling, non-ECC. If you’ve got spare desktop RAM lying around, it might work here. The UDIMM form factor is the interesting detail: Dell reserved SO-DIMMs for the Micro line and gave the SFF proper desktop sticks.