PC Labs has been testing solid state drives (SSDs) since the very first flash-based models, and we've benchmarked more than 100 internal drives since 2020. The WD Black SN8100 is the PCIe 5.0 victor, while the WD Black SN850X is the PCIe 4.0 champ. Early this year, Sandisk rebranded the WD Black and Blue lines as Sandisk Optimus SSDs—the WD Black SN850X becoming the Sandisk Optimus GX Pro 850X—while continuing to sell the WD Black versions, both direct and through retailers. A bit of context there: That drive was an early PCIe 5.0 model that supported only two PCIe lanes (designated a "PCIe 5.0 x2" drive), rather than the four lanes ("PCIe 5.0 x4") of the other PCIe 5.0 entrants. I tested it on our PCIe 5.0 testbed using the motherboard's own native heat spreader over the PCIe 5.0 slot.