SanDisk Extreme microSDXC UHS-I Memory Card Review

Transfer Speeds and Performance

To evaluate the performance of SanDisk’s Extreme microSDXC card, we plugged into a USB 3.0 FCR-HS3 card reader, connected to our Core i7-3960X / X79 Express-based test system, running Windows 8 Pro x64. In addition to monitoring performance during simple file transfers, we also ran a trio of benchmarks to see how the card handled different data types and transfer sizes. First up, ATTO’s Disk Benchmark.

As you can see in the image above, the SanDisk’s Extreme microSDXC card doesn’t hit its stride until the 64K mark, but when it does, performance actually exceeds SanDisk’s specified 80MB/s (read) and 50MB/s write speeds. According to ATTO, the SanDisk Extreme microSDXC card peaks at about 94.5MB/s and 61.7MB/s, for reads and writes, respectively.

CrystalDiskMark tells essentially the same story as ATTO. In this benchmarks, SanDisk’s Extreme microSDXC card tops out with 92.56MB/s and 61.45MB/s sequential reads and writes. Performance is also good in the 512K test, though the card struggles with smaller 4K transfers.

Finally we ran Anvil’s Storage Utilities SSD benchmark. This test is complete overkill for a microSDXC card, but if you want to full scoop on the SanDisk Extreme microSDXC card’s performance, there it is. As you can see, in the Sequential 4MB tests, the card has no trouble exceeding the speeds listed in card’s specifications.

We should also note that we monitored transfer speeds in a number of everyday usage scenarios, copying images and videos to and from the card, and it regularly exceeded SanDisk’s specifications. Read speeds of 88MB/s were common, with 58MB/s writes.

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