SanDisk is a well-known name in the flash memory industry. Founded in 1988, they developed the first flash-based SSD. They were later acquired by Western Digital in 2016, before being spun off as a public company in early 2025.
SanDisk is a name I’ve long been aware of, and one that — prior to this project — I was biased in favor of. I have a number of single-board computers that take microSD cards, and I typically defaulted to the SanDisk Ultra 16GB for their storage — and most of the time, had no issues with them. And since they’re such a major brand, I wanted to make sure they were properly represented in this project. I picked up this particular model after seeing that the packages for the SanDisk Extreme 32GB and the SanDisk Extreme 64GB advertised different sequential read speeds; similarly, the SanDisk Extreme PRO 32GB and the SanDisk Extreme PRO 64GB also advertised different sequential read speeds on their packages. I was curious to know if larger sizes of the SanDisk Ultra would show similar performance improvements when compared to its smaller siblings.
As it turns out, the answer was “yes”: this card performed nearly twice as fast (or sometimes more than twice as fast) in sequential read speeds compared to the SanDisk Ultra 32GB. All three scores came in somewhere between the 93rd and 99th percentiles. Sequential write speeds were generally better as well, although they were not as drastically improved as the sequential read speeds were. Random read speeds were worse than the 32GB version, while random write speeds were slightly better.
These cards carry the Class 10, U1, and A1 performance marks. Performance was good enough on all three samples to qualify for the Class 10 and U1 marks. Performance was good enough on two of the three samples to qualify for the A1 mark; and while the third sample fell a little bit short of the random write speeds required, on average these cards performed well enough to qualify for it.
On the endurance testing front:
- Samples #1 has survived 3,343 read/write cycles so far and has not yet experienced any errors.
- Sample #2’s first error was a single bit flip, in a single sector, during round 3,021. It has survived 4,213 read/write cycles in total so far.
- Sample #3 was doing just fine until round 1,327. During this round, it began experiencing almost constant I/O errors while trying to read back data. After about five days of this, it decided that it had had enough and stopped responding to commands altogether.
Overall? These cards did well in performance tests and were not very skimpy; however, I’d like to see more endurance data from these cards before I make a final call on them.
July 11, 2025