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Write speeds a third of read speeds, but still quite fast
on December 21, 2017
I'm using this in a Sony A7Riii camera and it works there. I tested its performance using a Sony MRW-S1 SDXC II USB3 card reader and the CrystalMark tool on Windows 10, comparing it to a Sony SDXC II card and a SanDisk SDXC I card.
The Amplim came close enough to the rated 285MB/s read speed - I got 271. But the write speed, for which no claim was made, was a third of that at 91MB/s. This surprised me.
Next up was the Sony card, which claims 300/299 read/write, and it delivered 289/257 - fine. The SanDisk card, which claims 90MB/s read (and no write speed is given) delivered 99/50.
Now, 91MB/s is still pretty darned fast, and it's probably adequate for 4K video and high-resolution photography, but write speeds are what limit you if you are trying to dump a lot of data to the card at once (like if I fill the camera's buffer with 10fps 42MP shots), and I would have preferred it to be faster. I think that if I were going to buy another card, I'd probably pay the (considerable) extra for the Sony. But if you're watching your pennies, the Amplim is just fine.
Edit December 22, 2017
I contacted Amplim to ask if the results I saw were expected, and they quickly responded to say that they were. The card meets the SD Association's V60 spec which is more than adequate for 4K video. (The SD Association says it can support 8K video!) The Sony card doesn't claim a V spec. The Amplim card conforms to the new SD 5.0 spec.