WD Polaris 3

The WD Polaris 3 (full designation: A101-000103-A1) is Western Digital's third-generation in-house NVMe controller, used in the WD Blue SN5000, WD Blue SN5100, and WD Black SN7100. Like earlier Polaris controllers it is an ARM Cortex-R design manufactured on 16nm, with 4 flash channels and 4 chip-enables per channel, but the channel bus rate has been raised to 2,400 MT/s, up from 1,600 MT/s on the Polaris MP16+.

Polaris 3 is a DRAM-less controller that relies on Host Memory Buffer (HMB), continuing the approach established with the original Polaris MP16. The 2,400 MT/s bus rate is compatible with both 162-layer BiCS6 NAND (as used in the SN5000 and SN5100) and the faster 218-layer BiCS8 (as used in the SN7100). The SN7100 additionally exposes NVMe 2.0 features through firmware, while the SN5000 and SN5100 operate under NVMe 1.4. Same controller hardware in both cases.