DDR3 ECC UDIMM vs RDIMM for Dell T320: Match rank, speed, and type or it won't boot

The T320 takes standard DDR3 ECC but is picky — you can’t mix UDIMM and RDIMM, and single- vs dual-rank DIMMs can’t share a channel. Speed must match at 1333MHz or 1600MHz, or everything clocks down to the slowest stick. Save the headache: buy a matched kit explicitly listed for the T320, or check Dell’s compatibility matrix.