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I have a Samsung Memory Card MicroSDXC 128GB PRO Plus UHS-I Grade U3 Class 10.

When testing it using CrystalDiskMark 5.5.0 x64 on Windows 10 using the Conceptronic Card Reader (product code CMULTITRVU3) via USB 3.0, I get the following Write speeds:

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This card is advertised as having transfer speeds of up to 95 MB/s for reading and up to 90 MB/s for writing.

Why am I getting such slow Write speeds and how can I fix this?

ProgrammerGirl
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1 Answers1

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Is this your card: https://www.samsung.com/us/computing/memory-storage/memory-cards/micro-sd-pro-128gb-memory-card-w-adapter-mb-md128da-am/ ?

If so, sequential write speed supposed to be at least 30MB/s because it is U3 grade. See this link. So you should try some test if card is normal.

  1. If you use front USB 3.0 panel of your PC, try using back side USB 3.0 panel instead. Some PC has poor performance/power draw problem on front USB panels.
  2. Try using another SD card reader or test it on your tablet/phone. Your reader supports USB 3.0 speed so it should handle 100 MB/s with no problem.
  3. Try contact your seller. They should replace/refund it unless it is too late.
  4. If above doesn't work, you should RMA it to Samsung. They provide 10 year warranty.

Hope this helps.

Kang Jeonghoon
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