Can you tell us how you tested? Secure Digital is very complicated internally and the speed rating is based on a very specific usage pattern. While I'm sure you understand this, many forms of "testing" can actually have the effect of slowing down the cards dramatically. On Sun, Feb 15, 2015 at 7:19 AM, Henry Baker <hbaker1@pipeline.com> wrote:
I purchased 4 32GB uSD cards from Costco yesterday, and found to my amazement that one of the devices was faulty: while the maximum write rate was >20 MB/s, its minimum write rate was 1.2 MB/s, with an average write rate of 5.1 MB/s.
While I suspect that this defective device will function correctly as a memory, I was amazed to find that perhaps 25% of these devices did not meet their speed requirement.
BTW, if you run Linux, there is a "benchmarking" function for the disk formatting program which is quite useful.
Now I'm going to have to test all of my SD cards in advance prior to using them.
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