Lexar is on a run, they've released two high-end drives in recent months. Back in May, we tested the Lexar NM800, which is powered by the Innogrit IG5236 controller, and now we have the NM790 for review. Today's drive uses the Maxiotech MAP1602 controller, which has gained a lot of fame recently, because it is a high-end design that achieves outstanding real-life performance, at excellent pricing, even without DRAM cache. We've previously reviewed drives using similar hardware configs, like the Acer Predator GM7 1 TB and the Netac NV7000-T 2 TB, today's review is our first review for a 4 TB model. While the Acer Predator GM7 is built using YMTC 128-layer 3D TLC flash, the Lexar NM790 uses the newer 232-layer variant, just like the Netac NV7000-T. A DRAM cache is not included, ensuring the low price point can be achieved.

Synthetic performance results of the Lexar NM790 are uninspiring. While sequential throughput does achieve the promised 5 GB/s, random writes are considerably lower than the competition. With just 28500 IOPS at 4K random write, the NM790 runs this test in SATA territory. I've reached out to Lexar to get more information on this behavior and will update this review accordingly. What I suspect is happening is that the drive's DRAM-less nature is responsible for these results. Our synthetic tests are performed with a relatively large 32 GB work area, whereas CrystalDiskMark uses a tiny 1 GB size, to show best-case results. Other drives using the same controller, but with 1 TB and 2 TB capacity, use a 32 MB Host-Memory-Buffer area. On the NM790 the HMB is sized at 40 MB, which is relatively smaller. Considering the 4 TB capacity, I would have expected 64 MB, or more. My guess is that this smaller HMB area makes it difficult for the controller to optimize random writes over a larger area. On drives with physical DRAM cache, the DRAM stores the mapping tables of the SSD (to figure out where a given piece of data is located). On DRAM-less drives that's handled by some controller magic, optionally with the help of the Host-Memory-Buffer area.

Still, despite some weak synthetic results, the real-life performance of the NM790 is outstanding. It is able to beat every single PCIe 4.0 drive out there, with the exception of the Samsung 990 Pro, which it is able to match—very impressive! That's why real-life testing is so important. We test actual applications, not replays of disk traces, and the drive is filled to 80% of its capacity, not an empty drive like most reviewers do. This approach puts additional strain on the various algorithms and the SLC cache, just like in real-life. We've seen this in several recent reviews: times have changed and you can no longer dismiss all DRAM-less drives—the controller and how well it handles this configuration matters, too.

Thanks to its pseudo-SLC cache, the NM790 can easily absorb large incoming write bursts. A SLC capacity of 270 GB is "good," maybe a bit small in absolute terms when considering that this is a 4 TB drive. Providing 270 GB in SLC mode, which uses three times the capacity, means that up to 810 GB, or 20% of 4 TB gets occupied by the SLC cache. Filling the whole drive completed at an average speed of 1.28 GB/s, which is good, but weaker than what the best PCIe 4.0 SSDs offer.

Our new power consumption tests are a great match for the Lexar NM790. It is the most energy-efficient drive in the whole test group—more than twice (!) as efficient as your typical Phison E18+Micron 176-layer drive, a bit less in writes, but still topping our charts. Our laptop idle power results show that the drive is able to enter its lowest power state with PCIe ASPM enabled. This was a problem on the Netac NV7000-T, but works on the Acer Predator GM7. It seems that there's still some firmware optimizations that Maxio can do for this scenario.

This high energy-efficiency helps the NM790 stay cool. In our thermal stress test we did see a bit of thermal throttling, but this test is much more difficult to complete than our previous SSD bench. We're now using a watercooling AIO—like many of you—which means there's only minimal airflow inside the case. Lexar includes a heat spreader foil on the drive, which is good enough, and ensures Sony PS5 compatibility, which requires some sort of cooler.

The Lexar NM790 is widely available, even the 4 TB version can be easily bought (unlike many other drives). With a price of $210 for the 4 TB version, the NM790 is priced competitively. While there's some 4 TB QLC drives available for $160-$180, these offer terrible write performance once the pseudo-SLC cache is full—not worth the trouble to save 20%. A strong alternative is the Silicon Power XS70 ($200, Phison E18+ Micron 176-layer). Many popular SSDs like the WD SN770, Solidigm P44 Pro and Atom 50 don't exist as 4 TB version. WD Black SN850X 4 TB costs $300 right now, way too expensive, just like the Kingston KC3000 for $355 and the PCIe Gen 5 Crucial T700 for $480. If you're willing to shop on AliExpress, then the Netac NV7000-T 4 TB for $160 could be an option, it's built using the same hardware as the Lexar NM790.