I recently bought an 8GB Kingston Fury DDR4-2666 module for my Dell Latitude 3410, which already had an 8GB SMART 1Rx8 PC4-2666V module installed. Each stick works normally by itself, but installing both causes an unusually long delay before the Dell logo appears. The first boot then reports that the memory configuration has changed, and the laptop fails to start properly afterward. The built-in memory diagnostics report no problems. I have already updated the BIOS and cleaned the module contacts, but neither helped. What could be causing the incompatibility, and what should I do to run 16GB reliably?
3 Answers
The fact that the laptop takes a long time before showing the logo suggests it is repeatedly training or retrying the memory configuration. Matching capacity and frequency alone does not guarantee compatibility; timing and module layout also matter. Check the exact supported memory specifications for the laptop and choose a second stick that matches the original SMART module as closely as possible.
Since each module passes diagnostics individually, the slots and sticks are probably functional. The failure is more likely caused by the pair not being able to agree on timings or other memory parameters. A BIOS update usually cannot resolve that kind of mismatch, so using two matching DDR4-2666 SO-DIMMs with the same specifications is the most reliable solution.
The two modules may be incompatible despite having the same advertised speed. Differences in memory timings, chip organization, voltage, or the module’s programmed profiles can prevent the laptop from initializing both sticks together. The Kingston Fury module may be configured with performance timings that the original OEM module does not share. The simplest fix is to replace it with another module that matches the original stick’s specifications, ideally an identical part or a matched 2×8GB kit designed for the Latitude 3410.

That makes sense. I’ll look for a matching module rather than mixing these two.