The ADATA Legend 840 is a solid-state drive in the M.2 2280 form factor, launched on November 3rd, 2021. It is available in capacities ranging from 512 GB to 1 TB. This page reports specifications for the 1 TB variant. With the rest of the system, the ADATA Legend 840 interfaces using a PCI-Express 4.0 x4 connection. The SSD controller is the IG5220 (RainierQX) from InnoGrit, a DRAM cache is not available. ADATA has installed 176-layer TLC NAND flash on the Legend 840, the flash chips are made by Micron. To improve write speeds, a pseudo-SLC cache is used, so bursts of incoming writes are processed more quickly. The cache is sized at 250 GB, once it is full, writes complete at 1900 MB/s. Copying data out of the SLC cache (folding) completes at 500 MB/s. Thanks to support for the fast PCI-Express 4.0 interface, performance is excellent. The Legend 840 is rated for sequential read speeds of up to 5,000 MB/s and 4,500 MB/s write; random IOPS reach up to 650K for reads and 600K for writes.
At its launch, the SSD was priced at 150 USD. The warranty length is set to five years, which is an excellent warranty period. ADATA guarantees an endurance rating of 650 TBW, a typical value for consumer SSDs.