Introduction

Western Digital (or simply WD) is the world's largest manufacturer of storage solutions, mostly known for their wide range of hard disk offerings. With their acquisition of SanDisk in 2016, WD became one of the largest manufacturers for flash storage, too.



In today's review, we'll be taking a look at the Western Digital WD Black SN770, which is a value-oriented SSD design with support for PCI-Express 4.0, but lacking a DRAM cache. We recently reviewed the PCI-Express 3.0-based WD Blue SN570 and were impressed by how well it handles all workloads, even those that usually require a DRAM cache chip, which sets the bar high for the SN770. For the SN770, and its PCIe 4.0 requirement, WD came up with a new 20-82-10081 controller and paired it with the latest 112-layer 3D TLC flash that SanDisk produces in a joint venture with Kioxia (ex-Toshiba), also known as BiCS5. A DRAM cache is not available, definitely to reduce manufacturing cost. To connect with the rest of the system, the PCI-Express 4.0 interface is used.

The WD Black SN770 comes in capacities of 250 GB ($53), 500 GB ($70), 1 TB ($115), and 2 TB ($250). Endurance for these models is set to 200 TBW, 300 TBW, 600 TBW, and 1200 TBW respectively. WD includes a five-year warranty with the SN770.

Packaging

The Drive

The drive uses the M.2 2280 form factor, which makes it 22 mm wide and 80 mm long.

On the PCB, you'll find the controller and just one flash chip; a DRAM cache chip is not installed, and the other side of the PCB is empty.


While most other M.2 NVMe SSDs transfer data over the PCI-Express 3.0 x4 interface, the WD Black SN770 connects to the host system using a PCI-Express 4.0 x4 interface, which doubles the theoretical bandwidth.

Chip Component Analysis

Almost nothing is known about the new SanDisk 20-82-10081-A1 SSD controller. It is a four-channel design, which obviously supports TLC and DRAM-less operation. Unlike the controller on the WD Blue SN570, it has support for the fast PCI-Express 4.0 interface.


The flash chip is 112-layer Kioxia/Toshiba BiCS, rebranded by SanDisk, who are now part of WD. WD operates a joint-venture with KIOXIA to produce these NAND chips.

Test Setup