Western Digital WD_BLACK SN850X 8000GB

SSD Description

The Western Digital WD_BLACK SN850X 8000GB represents the maximum density implementation of WD’s vertically integrated PCIe Gen4 architecture. It utilizes the proprietary SanDisk 20-82-10035-B2 controller—an iterative update to the original SN850 silicon—paired with BiCS5 112-Layer 3D TLC NAND. This high-capacity model requires a substantial DRAM cache to manage the expanded logical-to-physical mapping table, ensuring consistency in random I/O performance and sustained write workloads.

Field Notes: The 8TB variant is strictly a double-sided M.2 drive (components populated on both sides of the PCB), which can cause physical compatibility issues for ultra-thin laptops or consoles with restricted Z-height clearance. Thermal telemetry indicates the controller and NAND packages can reach throttling thresholds quickly under sustained loads; active cooling or a high-surface-area heatsink is strongly recommended for this capacity. The firmware includes Game Mode 2.0 to optimize predictive loading for DirectStorage APIs, though independent analysis suggests the performance impact is negligible in standard OS or productivity environments.

Key Specifications

• Interface: PCIe 4.0 x4 / NVMe 1.4
• Sequential Read: 7,200 MB/s
• Sequential Write: 6,600 MB/s
• Controller: WD Proprietary (20-82-10035-B2)
• NAND: SanDisk/WD BiCS5 112-Layer TLC
• DRAM Cache: Yes (DDR4)
• Endurance: 4,800 TBW
• Physical Layout: Double-sided M.2 2280
• Encryption: No hardware-based TCG Opal support (Consumer focused)

Hardware Alternatives

• Sabrent Rocket 4 Plus (8TB): The primary alternative in the high-density Gen4 space, using the Phison E18 controller paired with Micron 176-layer NAND. The SN850X generally offers superior throughput in low-queue-depth random reads compared to the E18 platform.
• Corsair MP600 PRO NH (8TB): Another Phison E18-based competitor. The WD_BLACK SN850X is distinguished by its custom controller logic, which tends to offer better power efficiency consistency than the E18 reference boards at this capacity tier.
• Samsung 990 PRO: A direct performance rival in the 1TB, 2TB, and 4TB classes; Samsung does not currently offer a direct competitor in the 8TB capacity tier, leaving the SN850X as one of the few single-drive 8TB options from a primary NAND manufacturer.