{
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-20",
  "slug": "sd-application-performance-class",
  "term": "SD Application Performance Class",
  "aliases": [
    "A1",
    "A2"
  ],
  "definition": "SD Application Performance Class specifies minimum random-access and sustained sequential-write performance under defined card and host conditions.",
  "note": "A1 specifies at least 1,500 random-read IOPS and 500 random-write IOPS; A2 specifies 4,000 and 2,000 respectively. Both include a 10 MB/s sustained sequential-write requirement under the specified test conditions [app].\n\nPhysical Layer Simplified Specification 7.10, section 4.16.1.2, requires cache use for A2. It permits SD Express and SDUC cards without command-queue support; when supported, the queue must be used. Other A2 card types require command queuing. With queue and cache disabled, an A2 card must support A1 conditions [spec].\n\nThese classes do not specify data retention or power-loss protection. A host must flush an enabled card cache before power-down; acceptance into the cache is not completion of that flush [cache].",
  "related": [
    "sd-capacity-family",
    "sd-speed-class",
    "sd-express",
    "iops",
    "cache-flush"
  ],
  "citations": [
    {
      "id": "app",
      "title": "SD Association brochure: application-performance minimums",
      "url": "https://www.sdcard.org/pdf/SDA_brochure_EN.pdf",
      "accessed": "2026-10-20"
    },
    {
      "id": "spec",
      "title": "SD Physical Layer Simplified Specification 7.10, section 4.16.1 (page 159)",
      "url": "https://www.sdcard.org/cms/wp-content/themes/sdcard-org/dl.php?f=Part1_Physical_Layer_Simplified_Specification_Ver7.10.pdf",
      "accessed": "2026-10-20"
    },
    {
      "id": "cache",
      "title": "SD Association: Applications in Action, cache flushing and A2 features",
      "url": "https://www.sdcard.org/press/thoughtleadership/applications-in-action-introducing-the-newest-application-performance-class/",
      "accessed": "2026-10-20"
    }
  ]
}