We have in our hands Micron's second consumer SSD equipped with 3D NAND flash. The BX300 is an entry-level model, available in capacities from 120GB to 480GB using Micron's 256Gb 32L 3D MLC. The series is based on a SM2258 Silicon Motion controller - the same used by ADATA in their SU900 and SX950 SSDs.

Micron introduced the Crucial MX100 in 2014, based on 16nm MLC NAND. The drive offered a great performance for its price. One year later the company came up with the Crucial MX200, which wasn't much of an improvement over the MX100. But at the same time, Crucial introduced the BX100, which used the same 16nm MLC but a cheaper Silicon Motion controller. The specific drive continued to offer good performance. In late 2015, Micron introduced the Crucial BX200 - their first SSD to use TLC NAND. The BX200 reduced price per GB, but sacrificed a great deal of performance and power efficiency in the process. The BX200 faced strong compatition from drives like the ADATA SP550 that used faster and cheaper SK Hynix TLC to undercut the BX200's pricing while offering somewhat better performance. In 2016 Micron's 3D NAND found its way to the Crucial MX300, which used a high-performance Marvell controller and the 3D NAND TLC. The MX300 thus was serving as successor to both the MX200 and BX200, and it has done the job well with good performance and far better power efficiency than any previous TLC SSD.

The Crucial BX300 is Micron's first MLC-based consumer SSD since the Crucial MX200. With the MX200, Micron used SLC caching on smaller capacities and had mixed success-peak performance was boosted, but at the cost of creating more background work for the controller that hurt sustained workloads. For the Crucial BX300, Micron is using relatively small fixed-size SLC caches. Sequential performance and random write performance are rated the same across all three capacities, while random read performance is reduced a bit for the 240GB and is cut in half for the 120GB model. The rated write endurance numbers are lower than the ostensibly higher-end MX300 model. The MX300 does have lots of overprovisioning with which to reduce write amplification, but the BX300 has a reasonable amount too and the advantage of inherently higher endurance from using MLC instead of TLC.