Technology & Positioning
Finally! A new PCI-Express Gen 5 SSD controller is available for consumer solid-state-drives. The new Innogrit IG5666 controller is designed to bring the fight to the Phison E26, which has dominated the PCIe Gen 5 SSD market for a year now. We recently tested the Team Group GE Pro, which pairs the IG5666 with YMTC TLC NAND, the ADATA Legend 970 Pro in today's review uses the same controller, but Micron 232-layer TLC NAND—the same as on the various Phison E26-based drives. A minor change is that the DRAM cache is from Samsung, vs Micron on the GE Pro—won't make much of a difference. While Phison started with 10 GB/s drives first and then upped the transfer rates to 12 GB/s and 14 GB/s over time, as faster NAND chips became available, Innogrit starts out with 14 GB/s right away, thanks to flash running at 2400 MT/s.

Synthetic Performance
Synthetic performance results of the ADATA Legend 970 Pro are highly impressive when it comes to 4K random IO. In this group of tests, the drive is the fastest that we've ever tested. It is one of the few that reaches over 100 MB/s at 4K Read QD1, which is one of the most important tests for an SSD, because it represents the vast majority of real-life transfers on consumer systems today. Sequential transfer rates are quite a bit lower than on the Phison E26 powered Corsair MP700 Pro. Especially 1M Sequential Read at QD1 can't impress, reaching just ninth place, with 4.6 GB/s. Interestingly, the NAND flash from Micron seems to do better with random IO, while sequential transfers are a little bit weaker than on YMTC. The differences are not huge though. For higher queue depths the drive does indeed achieve transfer rates of 10 GB/s+ for both read and write.

Real-Life Performance
Controller vendors have been optimizing their controllers for typical synthetic reviewer workloads on an empty drive. That's why it's important to also include real-life testing. We're even running those tests with the drives filled to 85% capacity, not empty. This approach puts additional strain on the various algorithms and the SLC cache, just like in real-life. Here the ADATA Legend Pro 970 Pro does well, but ends up a few percentage points behind the Corsair MP700 Pro. It reaches roughly the same performance levels as the best PCIe Gen 4 drives like the Samsung 990 Pro, Crucial T500, Solidigm P44 Pro and Lexar NM790. Even the aging Kingston KC3000 achieves the same performance. To be honest, that is a bit disappointing, I expected more. From other vendors we've been hearing that they are actively working on the firmware for their IG5666 drives, so this might improve over time. Looking at our test results, we can clearly see that write-heavy workloads do quite well on the 970 Pro, but read-heavy scenarios are just near the top, intermixed with the best Gen 4 drives. Of course that doesn't mean that the 970 Pro is "slow"—quite the opposite, it blazed through all our workloads, but given the Gen 5 marketing I expected more.

SLC Cache / Sustained Performance
ADATA's drive comes with an SLC cache size of 617 GB (or 90% in SLC mode), which is enough to soak up nearly all bursts of write activity. Once the SLC cache is exhausted, transfer rates still reach a respectable 1.7 GB/s. Filling the whole 2 TB capacity completed at a very good 2.4 GB/s, which is faster than nearly all Gen 4 SSDs, but still a few hundred MB/s behind the Corsair MP700 Pro, which reaches 2.8 GB/s in the same test. In this scenario, the Micron memory is a little bit faster than YMTC's TLC flash.

Power Consumption / Heat
Thermals of Gen 5 drives have always been challenging, with all either requiring an active fan-cooled solution, or a huge heatsink, or both. I really like that ADATA is bundling a preinstalled heatsink with their drive, which makes things simple, even for less experienced users who might be scared to install an M.2 heatsink. My favorite feature is that ADATA is powering the fan directly from the SSD, which eliminates the cable clutter that we've been seeing on all other Gen 5 SSDs on the market. While most people would expect such a capability as standard, this didn't turn out to be the case with Gen 5 consumer drives. The biggest challenge is that fans typically require 12 V to operate, but M.2 NVMe SSDs have just 3.3 V available. This means that step-up-circuitry is required on the customized PCB, in addition to the connector for fan power itself. Congratulations to ADATA for being the first SSD manufacturer to implement this solution.

Thermals of the ADATA Legend 970 Pro are excellent, temperatures are low and there is no thermal throttling. Unfortunately this is achieved only with lots of fan noise—the little fan runs at high speed at all times, even when the drive is completely idle. The drive itself consumes a lot of power. First, the Innogrit controller isn't that energy efficient, and the fan step-up circuit pushes power consumption even further, higher than on any other drive we ever tested. In idle, we measured over 5 W, which is more than most Gen 4 drives at full load! Even in a laptop scenario, the power draw was 3 W—that's going to drain your battery in no time. When fully loaded, the drive hits 13 W, 2 W less than the YMTC equipped Team Group GE Pro, despite the extra fan. Looks like the Micron NAND flash is more energy-efficient than YMTC's offering.

Pricing & Alternatives
ADATA tells us that the price for the Legend 970 Pro 2 TB is $300, which is way too high. The direct competitor, which uses the same controller, the Team Group GE Pro 2 TB is currently listed online for $260, but comes without a heatsink. At $300, the Legend 970 Pro is more expensive than most Gen 5 2 TB drives using the Phison E26 controller, which start at around $230. No doubt, ADATA's custom PCB design, which powers the fan directly is awesome, but given the other results in this review, I find it impossible to recommend any IG5266 drive, unless they are much cheaper. If the price reaches less than $200 it could become an interesting alternative to Phison-powered drives, or a lot of firmware improvements must be found. Interestingly, the ADATA Legend 970 non-Pro is the most affordable PCIe Gen 5 drive at this time—just $230—I'd take that over the 970 Pro any day. Strong competition comes from the best PCIe Gen 4 drives, which are just as fast, at much lower pricing. My top candidates here are Lexar NM790 ($135), Samsung 990 Pro ($170), Crucial T500 ($145), Solidigm P44 Pro ($140), which are all cheaper and not that much slower. If you are shopping not only for performance, but also for value, then you should definitely consider the WD SN770 ($120), too.