The arrival of the new Ryzen 7000 family of CPUs 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, then, 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 a revision of the existing non-X WD_Black SN850 (opens in new tab). Which is not 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 setup 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 had with or without a heatsink, with the latter option costing around $30/£25 cheaper.

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 no specific details are provided.

The unit's TLC flash memory chips have also been upgraded from 96-layer TLC chips to a newer 112-layer technology, although that's still some way behind the fancy new 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 that write speeds have been increased from 7,000MB/s to 7,300MB/s, while reads have increased from 5,300MB/s to 6,300MB/s. That’s pretty much in the same ballpark as the SK Hynix drive. Moving on to IOPS, the old 1TB SN850 achieved 1 million reads and 720K writes. WD says the revised X model is now good for 1.1M and 800K, respectively. Not bad, though 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, and is therefore the same as the old non-X and several other 1TB drives from big brands like the Samsung 980 Pro, although the SK Hynix monster inevitably has the edge with a 750TB rating. In reality, you're looking at 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 loading times thanks to a so-called “read look-ahead” algorithm that predictively caches game data. It now runs automatically, detecting when games are loaded. How much of a difference this kind of feature actually makes in the real world is notoriously difficult to pin down. But it’s unlikely to be revolutionary.

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What we can say for sure is that peak sequential transfer rate is pretty much in line with WD's numbers. CrystalDiskMark results are therefore just above the claimed 7,300 MB/s for reads and also 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. That’s 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 huge gains in system-wide performance metrics like the 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. That should be enough for most, if not all, users.

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All of this means that 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. Thankfully, this new X model is unequivocally cooler.

For most PC applications, this probably won't matter. But for small form factor rigs and perhaps a gaming laptop, every little bit 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.