{
  "slug": "u3",
  "term": "U.3",
  "aliases": [
    "SFF-TA-1001",
    "U.3 SSD"
  ],
  "definition": "U.3 is the SFF-TA-1001 universal x4 link arrangement for SFF-8639 drive bays that can accommodate PCIe, SAS, or SATA devices with appropriate host support.",
  "note": "SFF-TA-1001 defines the U.3 link used in tri-mode backplanes. Sharing the SFF-8639 connector does not make U.2 and U.3 equivalent. A bay accepting different protocols does not mean that an individual NVMe SSD also speaks SAS or SATA. [c2]\n\nCompatibility is directional. Revision 1.1 requires compliant U.3 PCIe devices to operate in U.2 (Quad PCIe) and U.3 slots, within the available lane width. It does not require a U.3 slot to operate U.2 devices. Verify the particular drive, controller and backplane documentation; systems may implement additional compatibility. [c1]",
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "related": [
    "u2",
    "nvme",
    "enterprise-ssd",
    "pcie-lanes"
  ],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "c1",
      "title": "SNIA SFF-TA-1001 Rev 1.1: Universal x4 Link Definition for SFF-8639, section 1 and Table 1-1",
      "url": "https://members.snia.org/document/dl/26900",
      "accessed": "2026-10-18"
    },
    {
      "id": "c2",
      "title": "KIOXIA: Preparing for Your Storage Future with NVMe SSDs, January 2020 Rev 1.1",
      "url": "https://americas.kioxia.com/en-us/business/resources/best-practices/preparing-storage-nvme-ssds.html",
      "accessed": "2026-10-18"
    }
  ],
  "provenance": [
    "The compatibility rule is a reading of SFF-TA-1001 Rev 1.1, not a benchmark or hardware certification. [c1]",
    "The U.3 name is linked to SFF-TA-1001 by KIOXIA's technical document. [c2]"
  ],
  "updated": "2026-10-18"
}