If this review looks like déjà vu to you, then you are not mistaken. We tested the NM790 4 TB in August and gave it a glowing review—excellent performance at fantastic pricing. After our review went live, several readers contacted me and asked if I had any thoughts on performance of the 2 TB drive, because that's the model they were interested in most. I never doubted that performance would be similar to the 4 TB model, but I wasn't 100% sure, because the 4 TB model runs with 40 MB Host-Memory-Buffer for the mapping tables of the SSD, which is a limitation of the MAP1602 controller. The 2 TB model in this review has 32 MB HMB, which is not half, but 80%. Besides the change in HMB, everything else is as expected. The 2 TB model uses the same MAP1602 controller as the 4 TB version, and it's also built using 1 TB YMTC 232-layer NAND flash chips—there's just two instead of four. A DRAM cache is not included, ensuring the low price point can be achieved.

Synthetic performance results of the Lexar NM790 2 TB model are virtually identical to the 4 TB design, with the exception of random writes. Our 4K random result, which focuses on tests at low queue depths (just like real-life) shows a huge improvement over the 4 TB model: 67,878 IOPS vs 28,586. That's the HMB size making a difference. It looks like 32 MB is a much better match to keep all (most?) mapping tables for the 2 TB capacity in HMB. The 4 TB / 40 MB combo probably had to go back to flash to pull out certain bits of the mapping table when needed. Just to clarify, just like the DRAM cache, the HMB does not store incoming or outgoing data, but the mapping tables of the SSD. These tables contain information for the controller where to find a certain piece of data that's spread out among multiple chips to achieve higher bandwidth.

Interestingly, most all of our real-life test results are within margin of error on both drives. This just confirms that typical consumer applications really don't perform enough random writes to make DRAM essential. We're also testing with all drives filled to 80% capacity (not a mostly-empty drive), to make things even harder for the controller and its algorithms. There is a bunch of tests that run slightly faster, but it's nothing you'd ever notice in real-life. Still, at the end of the day, the NM790 gains 1% in performance over the NM790 4 TB, which makes it the fastest Gen 4 SSD we have ever tested, matching the much more expensive Gen 5 SSDs. Yup, you read right. A DRAM-less Gen 4 SSD is matching the mighty Phison E26 controller, which even has a physical DRAM chip available—very impressive. Of course tests that focus on sequential transfer like our "Game Copy" workloads run much faster on the PCIe 5.0 drive, but other tests run a little bit faster on the NM790, thanks to Maxiotech's algorithms, leading to a tie overall.

Thanks to its pseudo-SLC cache, the NM790 can easily absorb large incoming write bursts. A SLC capacity of 280 GB is "good," maybe a bit small when compared to other 2 TB drives. Providing 280 GB in SLC mode, which uses three times the capacity, means that up to 840 GB, or 40% of 2 TB gets occupied by the SLC cache. Filling the whole drive completed at an average speed of 1.45 GB/s, which is very 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. Compared to the 4 TB model, writes consume a little bit less power, probably because there's fewer NAND chips to power.

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 for nearly all use cases. Today, the company announced that they are coming out with a heatsink model of the NM790, which also adds Sony PS5 compatibility.

The Lexar NM790 is widely available, the 2 TB version sells at a highly impressive $110, which makes the drive the most affordable high-end option currently on the market. There's a bunch of strong alternatives though, like the WD Black SN770 ($100) and the Silicon Power XS70 ($100, Phison E18+ Micron 176-layer). The Samsung 990 Pro is a little bit on the expensive side ($130), just like the WD SN850X ($150).