RAM not detected or running slowly: what to check
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If some RAM is missing or the kit is running below its advertised profile, start with the fitted slots and the BIOS reading. Get the full capacity working at defaults, then enable the memory profile and check stability.
For a confirmed memory replacement or capacity change, use the RAM buying guide. Match the exact kit and board support before applying a faster profile.
Check BIOS-reported capacity and module information, then compare Windows. Identify whether a module is missing, memory is reserved, or only the speed differs from the kit’s profile.
Memory tools can report a clock figure that differs from the advertised effective transfer rate. Read the tool’s definition before assuming the RAM is running at half its intended rate.
Check seating and positions
Disconnect mains before reseating. Confirm latches are engaged and use the manual’s recommended first pair of slots. Check that you installed the intended matched kit.
Test one module in the recommended position at default settings, then compare another in the same position. If needed, follow the manual’s supported slot-testing route and record each result.
Return to a stable baseline
Use the documented BIOS procedure to remove optional profiles or tuning. Allow expected training time. Check support information for the exact CPU, kit and DIMM arrangement.
Get the Crucial kit stable at its default settings before enabling the faster profile. A successful boot does not establish stable operation throughout normal use.
Treat mixed kits as a new configuration
Modules sharing a brand or speed label are not necessarily a validated matched set. Four modules can require different settings from two.
Do not keep raising voltage or adjusting many timings without a supported procedure. A single matched kit at appropriate capacity may be easier to validate, but diagnose seating and support first.
Before requesting a replacement
Save kit codes, board revision, firmware, default/profile results and your module/slot comparisons. Use that record with manufacturer support.
For buying advice, follow the RAM guide. For repeated restarts, use boot diagnosis.
Record the module and slot results separately
| Check | Record | What it distinguishes |
|---|---|---|
| BIOS capacity | Detected total and individual module information. | Hardware detection versus a Windows reading. |
| Default boot | Outcome with optional profiles removed. | Baseline fault versus tuning instability. |
| Single-module comparison | Each module in the documented test position. | A repeatable module-related difference. |
| Supported slot comparison | Result following the manual’s allowed sequence. | A slot/population-related difference. |
Keep power disconnected while reseating and follow the board’s handling instructions. Change one variable at a time. A single-module test should use the position specified by that board, rather than whichever slot is easiest to reach.
Low speed, training and mixed kits
Use the MHz/MT/s explanation before treating a halved clock reading as a fault. Compare the baseline and intended XMP/EXPO settings using the same units. Allow the documented training time after changing modules or settings.
If trouble began after adding a second kit, compare the new mixed/four-DIMM configuration with the original working arrangement. A profile that worked before the capacity change does not establish support for the new population.
For a confirmed replacement, use the RAM shortlist at the capacity your workload needs. Preserve the module codes and test record for manufacturer support.