Problem
A UHS-II card is inserted into a UHS-I reader and the resulting slower transfer is mistaken for SSD performance degradation.
Solution
Root Cause / Diagnostic:
UHS-II cards feature an extra row of electrical pins capable of 300MB/s data rates. Plugging a UHS-II card into a legacy single-row UHS-I reader forces the card to fall back to the legacy SDR104 bus mode, capping transfer throughput at ~90MB/s and leading operators to falsely suspect destination drive throttling.
Actionable Fix:
1. Card Reader Verification: Replace the reader with a certified UHS-II dual-row card reader (e.g., Kingston MobileLite Plus, ProGrade Dual-Slot).
2. Interface Link Identification: Check device manager / system profiler to verify whether the reader controller is negotiating UHS-II or UHS-I bus timing.
3. Benchmarking Baseline: Benchmark card read throughput using CrystalDiskMark; confirm read speeds reach >250MB/s on UHS-II media.
Pro Tip:
Look closely inside your SD reader: if there is only one row of gold contacts inside the slot, it's a UHS-I reader that is cutting your UHS-II offload speeds by more than two-thirds.
UHS-II cards feature an extra row of electrical pins capable of 300MB/s data rates. Plugging a UHS-II card into a legacy single-row UHS-I reader forces the card to fall back to the legacy SDR104 bus mode, capping transfer throughput at ~90MB/s and leading operators to falsely suspect destination drive throttling.
Actionable Fix:
1. Card Reader Verification: Replace the reader with a certified UHS-II dual-row card reader (e.g., Kingston MobileLite Plus, ProGrade Dual-Slot).
2. Interface Link Identification: Check device manager / system profiler to verify whether the reader controller is negotiating UHS-II or UHS-I bus timing.
3. Benchmarking Baseline: Benchmark card read throughput using CrystalDiskMark; confirm read speeds reach >250MB/s on UHS-II media.
Pro Tip:
Look closely inside your SD reader: if there is only one row of gold contacts inside the slot, it's a UHS-I reader that is cutting your UHS-II offload speeds by more than two-thirds.