Good performance for a startlingly low price make this drive a game-changer for bargain users. But it’s a dud when it runs out of cache.

The Intel SSD 660p will shake up the low end of the NVMe market with very good performance at an unprecedented price, even though write speeds can drop precipitously to 100MBps when very large amounts of data are written to the drive, or when it begins to fill up. Note that the 512MB version offers significantly slower performance.
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https://www.pcworld.com/article/3294356/intel-ssd-660p-review-quad-level-cell-qlc4-bit-nand-debut.html