CrystalDiskMark Results Lower Than Expected: A Troubleshooting Checklist
Low benchmark numbers can come from interface limits, thermals, test settings, power mode or background activity.
Confirm the exact drive and slot
Model capacity matters, and NVMe slots can differ in PCIe generation or lane configuration. A fast SSD in a slower slot cannot exceed the slot’s transport limit.
Match the test profile
Compare like with like. Test size, number of passes, queue depth, thread count and units must be the same before two screenshots can be compared fairly.
Watch temperature
NVMe performance can fall as the controller heats up. If the first run is fast and later sustained runs slow down, log temperature and allow a cool-down before assuming a hardware defect.
Check free space and cache state
A nearly full SSD has less working room, and sustained writes may overflow an SLC cache. Both can reduce write performance.
Eliminate background I/O
Windows Update, antivirus scans, cloud sync and indexing can compete with a benchmark. Test from a reasonably idle system and repeat the run rather than trusting one outlier.