I just bought [10] 32GB US SDXC™ UHS-I card and it is slow why??

I  just bought [5] 32GB US SDXC™ UHS-I card and it is slow why??.. I use CrystalMark to test it on windows 7 using a USB adapter that came with it. I thought this would be at leasty 30mb/sec but when I tested it… it was barely even 10MB/sec… I feel scammed. Please let me know what is going on. We plan to use this on Sony Nex5n cameras for an expedition. We tested other class 6 32gb cards and they were not even rated at Class 10 but were consistently around 19-22mb/sec read and write. Please advise.

Phillip K

what type of reader are you using to test the cards? the reader and hosts will have to be UHS compatible. if not you will not see the full speed. 

I feel your pain…same thing happened to me…just FYI, 32GB is SDHC (64GB and above is SDXC)…i am currently in the process of RMA with my latest SanDisk Extreme SDHC card. I purchased from an authorized dealer, and after experiencing (and measuring with ATTO) the slow speeds, went through a very quick, thorough email convo to confirm my findings. Do yourself a favor and send an email with your concerns to SanDisk. They will follow up quickly. After sending the slow card to them, they say I’ll be receiving the new correct card tomorrow. Fingers crossed :smiley:

My guess is HUGE amounts of confusion over product IDs…there are at least 3 new product IDs for the newest cards, with little to tell them apart at first glance. And there are slight differences on the cards themselves, even those with similar names and speeds. The website is out of date, which should be a HUGE embarrassment as well. If we are confused, you can bet the production facilities are scratching their heads too. Who knows what they’re sending to the retailers?

It’s time for SanDisk to rethink the naming convention on their cards…why not just SanDisk Extreme32 and Extreme32 UHS? Anyone with half a brain can infer there is a difference, et voila! No more confusion…

Anyway, best of luck…hope they get your card troubles sorted out!


this is more than likely not a bad card. you MUST have a reader that supports UHS I to see the full speed. Readers that use PIO mode will not see the full speed and even though PIO support up to 25MB/s these cards do not perform that fast in PIO readers. simply put you will need a new reader to see the full speed. Either the SDDR-289 USB 3.0 reader or the extreme Pro Express card adapter are the only ones that will do it. 

i heard that earlier today…my concern is not with top speed, but with sub par speed…not only in uhs1 but non uhs 30mb/s cards…they are both too slow in write speed…unless you find 7mb/s acceptable, i haven’t heard a reasonable excuse for the issue…is it possible that sandisk purposely hobbled their cards and failed to advise nor recommend their card readers when designing and marketing the cards? buy our fast cards…i mean, slow but fast cards…i mean, slow but fast in our card readers…sounds ridiculous to you too i bet.

OK, I am confused.

If I have a non-UHS compliant device, should I be purchasing an older, non-uhs compliant card?

I was under the impression that UHS is an additional feature.

I thought that if I put a UHS card in a non-UHS device, it would operate at standard speeds… ie: it should still be as fast as a non-UHS card in the non-UHS device.  Correct?


Anybody know?

The card will work it will just work at a slower speed. The UHS cards will not however work at 30MB/s their Max speed will be more around 20MB/s in non UHS devices. UHS and non UHS product have different hardware and firmware. While they are backwards compatible they are not the same and the performance will differ slightly. 

OK… so if I have a non-UHS compliant device, would I get better performance with an older, non-uhs compliant card? 

Or would the newer UHS compliant card be better?

Anyone have any experience with this?