PNY CS900 480GB

A TLC SSD for QLC money? There must be a catch…

SOLID STATE STORAGE prices have dropped off a cliff. We’re now talking sub-$100 for a 1TB drive, and below $50 for 500GB. That’s not far off half the price drives were going for six months ago. Insane.

Or it would be if such drives were easy to recommend. Often, they’re not. Broadly speaking, entry-level SSDs fall into two categories. First are drives based on TLC NAND memory from brands you’ve never heard of. Rolling the dice on one of those is an unnerving experience.

The other option is a QLC drive from a more reassuring manufacturer. Problem is, the underlying performance of QLC NAND memory is garbage. Given all such drives operate with some level of SLC cache, one can debate how often the true performance of the bulk of the drive will be exposed. But it’s certainly off-putting.

With all that preamble processed, this PNY drive actually looks pretty appealing. At $69 for this 480GB model, it’s not the cheapest, but it is competitive. More to the point, PNY isn’t some obscure outfit cranking out lashed-up drives thrown together from factory floor sweepings. Oh, and it’s based on TLC NAND, rather than that QLC gunk. Result.

In that context, the fact that the CS900 brand originally came out a few years ago probably doesn’t matter. On paper, it certainly looks promising. What’s not to like about 550MB/s reads and 500MB/s writes from a SATA SSD?

Indeed, many of our benchmark results look quite acceptable. Granted, the CS900’s 367MB/s sequential write performance is well down on PNY’s claims, but it’s just fine for a budget SATA drive. Random access 4K performance looks decent, too. By decent we mean orders of magnitude better than a mechanical hard drive.

However, the wheels fall off this particular train in our real-world 30GB internal file copy benchmark. Not far off five minutes is tragic. Moreover, it quickly became obvious that this drive can’t sustainably deliver on PNY’s claimed performance figures during our pre-test drive prep routine. The CS900 can only maintain its peak sequential performance for a few seconds before dropping down to a lowly 50MB/s.

Funnily enough, that’s reminiscent of all the QLC SSDs we’ve tested, albeit those drives sustain their peak performance for longer before falling back to the inherent throughput attainable by QLC NAND cells. As for the whys and wherefores, part of the explanation is that the CS900 is a DRAM-less drive. Instead of inserting a DRAM cache between the controller and the NAND, the CS900 can only rely on 32MB of SRAM built into its Phison S11 controller chip.

Speaking of DRAM-less SSD controllers, it’s worth noting that such implementations also raise question marks about drive longevity. A DRAM cache doesn’t just boost performance; it also dramatically reduces wear on the flash cells. To PNY’s credit, the CS900 is backed by a reassuring three-year warranty, which is all you can ask for at this price point. But even if PNY is fully co-operative in the event of a failure, you still have the possibility of significant downtime and data loss.

As promising as the CS900 looks on paper, then, the reality sails straight past underwhelming and right into avoid at your peril territory. Our advice? If you must go uber cheap, a premium brand QLC drive is the preferred option. Better yet, spend a bit more.