The arrival of the new Ryzen 7000 CPU family means that PCIe Gen 5 is now a thing on both AMD and Intel platforms. But let's be real. Your current PC almost certainly doesn't have a PCIe 5.0 M.2 slot. Enter the new WD Black SN850X, a sort of last hurrah for Gen 4 SSDs.

Reviewed here in its 1TB configuration, the WD_Black SN850X isn't exactly a new drive, more of a revision of the existing non-X WD_Black SN850 (opens in new tab)Which isn't bad. After all, the old SN850 was one of our favorite M.2 SSDs. (opens in new tab)It's fast, competitively priced, and backed by one of the best brands in storage. The old SN850, however, ran a bit hot.

The new WD Black SN850X has a few solutions for this. First, our test configuration is clad head-to-toe in WD's signature shield-style cooling. While this cooling solution was optionally available on the old SN850, the new WD drive's revised thermal profile is not. This is specific to the SN850X.

Of course, if your motherboard comes with its own M.2 SSD cooling kit, you might not want to pay extra for a self-cooling SSD. WD can easily accommodate that. The new X model, like its predecessor, can be purchased with or without a heatsink, the latter option costing about US$30 / £25 less.

Indeed, in many ways, this new X model is a dead ringer for the existing SN850. We're talking four lanes of PCIe Gen 4 connectivity in the now-ubiquitous M.2 2280 form factor. But the 1TB model reviewed here is now the entry-level option. There's no longer a 512GB model. Additionally, WD's internal controller chip has been revised, though specific details aren't provided.

The drive's TLC flash memory chips have also been upgraded from 96-layer TLC chips to a newer 112-layer technology, though this still lags slightly behind the new, more sophisticated 176-layer NAND from Micron and SK Hynix. However, the new SN850X boasts higher claimed performance than before, so the question is whether it now has what it takes to compete with Gen 4 speed freaks like the SK Hynix Platinum P41.

For this 1TB model, WD estimates write speeds have increased from 7,000 MB/s to 7,300 MB/s, while reads have increased from 5,300 MB/s to 6,300 MB/s. This is roughly in the same ballpark as the SK Hynix drive. Moving on to IOPS, the old 1TB SN850 achieved 1 million reads and 720,000 writes. WD says the revised X model is now good for 1.1M and 800K, respectively. Not bad, although the SK Hynix produces read and write IOPS of 1.4M and 1.3M.

As for write endurance, this 1TB drive is rated at 600TB, making it the same as the old non-X and several other 1TB drives from major brands like the Samsung 980 Pro, though the SK Hynix monster inevitably has the edge with a 750TB rating. In reality, you're getting hundreds of gigabytes of writes daily for over five years anyway.

A bit more specific to this WD drive is the latest version 2.0 of the company's Game Mode drive management software. WD claims it improves game load times thanks to a so-called "read look-ahead" algorithm, which predictively caches game data. It now runs automatically, detecting when games are loaded. How much of a real-world difference this kind of feature actually makes is notoriously difficult to pinpoint. But it's unlikely to be revolutionary.

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What we can say for sure is that peak sequential transfer rate is roughly in line with WD's numbers. CrystalDiskMark results are therefore just above the claimed 7,300 MB/s for reads and 6,300 MB/s for writes, making this a very fast 1 TB drive. Only the 2 TB models, including the aforementioned SK Hynix P41, are faster.

Reduced operating temperatures are another clear benefit of this new drive. The old SN850 reached 77°C. The new drive only reaches 58°C under sustained load. This is a worthwhile improvement. Elsewhere, the gains are less obvious, although the SN850 was already a great drive. The 4K random access results are a bit disappointing, showing little to no improvement. Likewise, don't expect major gains in system-wide performance metrics like PC Mark 10.

Finally, the SLC cache allocation of the new SN850X hasn't changed. So, with an empty drive, you get about 300GB of writes at peak performance before the underlying performance of the TLC NAND chips is exposed. This should be sufficient for most, if not all, users.

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All of this means the new WD Black SN850X isn't exactly a revolutionary advancement. In fact, in the real world, you'll have a hard time noticing the difference from the existing SN850 drive. But that's because the SN850 is a very good SSD. The only exception to this is operating temperatures. Fortunately, this new X model is unequivocally cooler.

For most PC applications, this probably won't matter. But for small form factors and perhaps a gaming laptop, anything can certainly help. On that note, for most applications, we'd probably go for the cheaper bare unit rather than this more expensive model with its heatsink. After all, the revised SN850X is inherently a cooler thing.