# SDHC class 10 UHS-1 card behaving like class 6 card

**URL:** <https://forums.sandisk.com/t/sdhc-class-10-uhs-1-card-behaving-like-class-6-card/34846>\
**Category:** SD | microSD | CFast | CFexpress | CompactFlash\
**Created:** [April 14, 2013, 7:36am UTC](https://forums.sandisk.com/t/sdhc-class-10-uhs-1-card-behaving-like-class-6-card/34846 "2013-04-14T07:36:27Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![sikin](https://avatars.discourse-cdn.com/v4/letter/s/58f4c7/32.png) [@sikin](https://forums.sandisk.com/u/sikin)\
**Post date:** [April 14, 2013, 7:36am UTC](https://forums.sandisk.com/t/sdhc-class-10-uhs-1-card-behaving-like-class-6-card/34846/1 "2013-04-14T07:36:27Z")

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i recently bought a Sandisk extreme SDHC UHS-1 class 10 card (16 GB one) from flipkart. Soon after opening the package when i tested this card for its performance with Laptops inbuilt card reader, it behaved like normal class 6 card with read/write speeds of around 6MB/s (in b/w 5-6).&nbsp;

I tested it in several scenarios, with file format change (fat32/exFat, NTFS), with 1.26gb file transfer (from and to card), using CrystalDiskMark 3.0.2. Everywhere it didnt go beyond 6MB/s read/write speed.

card reader used: inbuilt one

Laptop: dell XPS l502x, core i7 2670, 8gb ddr3 ram, 7200rpm hdd…

Please help me on this. Is there any problem with card? or some other issue…

 ![](https://global.discourse-cdn.com/sandisk/original/2X/f/f5db2e2889c40184d187ec27eaccda765630f495.jpeg)

 ![](https://global.discourse-cdn.com/sandisk/original/2X/d/d416f206ec08af55e5cfd8fa3b33620057c42b13.jpeg)

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**Author:** ![ghostofcain](https://avatars.discourse-cdn.com/v4/letter/g/a5b964/32.png) [@ghostofcain](https://forums.sandisk.com/u/ghostofcain)\
**Post date:** [April 15, 2013, 11:56am UTC](https://forums.sandisk.com/t/sdhc-class-10-uhs-1-card-behaving-like-class-6-card/34846/2 "2013-04-15T11:56:13Z")

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What speed card does your laptops inbuilt reader support?

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**Author:** ![sikin](https://avatars.discourse-cdn.com/v4/letter/s/58f4c7/32.png) [@sikin](https://forums.sandisk.com/u/sikin)\
**Post date:** [April 15, 2013, 3:27pm UTC](https://forums.sandisk.com/t/sdhc-class-10-uhs-1-card-behaving-like-class-6-card/34846/3 "2013-04-15T15:27:12Z")

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Cant exactly tell that thing, but it does support SDHC/SDXC cards.  
And main thing is this, that even with 4gb sony class 4 card i am getting minimum 8-10MB/s Read/Write speeds.

With 4 gb sandisk class 6 card its 12-15MB/s read/write speeds…  
But with 16GB class 10 UHS-1 card it no more than 6MB/s ☹

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<div class="post-metadata">

**Author:** ![sikin](https://avatars.discourse-cdn.com/v4/letter/s/58f4c7/32.png) [@sikin](https://forums.sandisk.com/u/sikin)\
**Post date:** [April 16, 2013, 5:05pm UTC](https://forums.sandisk.com/t/sdhc-class-10-uhs-1-card-behaving-like-class-6-card/34846/4 "2013-04-16T17:05:21Z")

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Issue resolved.  
Problem was, i do have UHS-1 compatible reader but it was running on default windows 8 drivers.

As soon as i installed its drivers, it worked like charm with R/W speeds of ~40-46MB/s.  
when on stock drivers, it wont go beyond 6MB/s.&nbsp;

When i tested it on an older laptop with SD/HC reader it gave R/W speeds ~ 14-20MB/s.

My conclusion:

UHS compatible reader: actual driver for reader required else it wont even run on minimum speed of 10MB/s for class 10 card. With proper drivers installed you get maxed out speeds (~ 45MB/s)

non-UHS compatible reader: even w/o required drivers, on default windows drivers it gives R/W speeds of min 10MB/s