SD Card Notes

README.md

SD Card Specifications

• SD Card Specifications
  • Capacity Types
  • Speed Classes
  • Bus Interfaces

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Capacity Types

Refers to the maximum capacity.

• SD: Capacity up to 2GB.
• SDHC: Capacity over 2GB up to 32GB.
• SDXC: Capacity over 32GB up to 2TB.
• SDUC: Capacity over 2TB up to 128TB.

Speed Classes

Refers to the minimum sequential write speed.

• Speed Class: Initial speed class.
  • (2): 2MB/sec
  • (4): 4MB/sec
  • (6): 6MB/sec
  • (10): 10MB/sec
• UHS Speed Class: Newer & faster speed class.
  • U1: 10MB/sec
  • U3: 30MB/sec
• Video Speed Class: Optimized speed class for video recording.
  • V6: 6MB/sec
  • V10: 10MB/sec
  • V30: 30MB/sec
  • V60: 60MB/sec
  • V90: 90MB/sec
• Application Performance Class: Optimized speed class for applications (input/output operations per second).
  • A1:
    • Minimum Random Read: 1500 IOPS
    • Minimum Random Write: 500 IOPS
    • Minimum Sustained Write: 10MB/sec
  • A2:
    • Minimum Random Read: 4000 IOPS
    • Minimum Random Write: 2000 IOPS
    • Minimum Sustained Write: 10MB/sec

If a card is rated for a multiple of each listing, then the highest value is the rating of the card (eg. (10), U3, V30, A2 = 30MB/sec).

Bus Interfaces

Maximum potential transfer speed.

• Default: 12.5MB/sec
• High Speed: 25MB/sec
• UHS-I: 104MB/sec
• UHS-II: 312MB/sec (Has a second row of connectors.)
• UHS-III: 624MB/sec (Has a second row of connectors.)
• Express: 985MB/sec (First Row: UHS-I / Second Row: PCIe Gen 3 with NVMe)