SD Card vs. SD Speed Classes
Comparing 2 standards across 13 specifications. 13 key differences identified.
The SD Card (Secure Digital) is the global standard removable flash memory form factor established in 1999 by Panasonic, SanDisk, and Toshiba (SD Association). Measuring 32.0 × 24.0 × 2.1 mm, it spans capacity generations from original SDSC (up to 2GB) and SDHC (up to 32GB) to SDXC (up to 2TB) and SDUC (up to 128TB).
SD Speed Classes are standardized performance metrics defined by the SD Association to guarantee minimum sustained write speeds for uninterrupted video recording and random IOPS execution for applications. They encompass legacy Speed Class (C2–C10), UHS Speed Class (U1/U3), Video Speed Class (V6–V90), and Application Performance Class (A1/A2).
Specification Comparison Table
13 Parameters| Parameter / Spec | ||
|---|---|---|
|
Governing Body
|
SD Association (SDA) | — |
|
Physical Dimensions
|
32.0 mm × 24.0 mm × 2.1 mm | — |
|
Pin Configurations
|
9 pins (UHS-I / Legacy) / 17 pins (UHS-II / UHS-III dual-row) / 19 pins (SD Express) | — |
|
Capacity Standards
|
SDSC (≤2GB), SDHC (4–32GB), SDXC (64GB–2TB), SDUC (2TB–128TB) | — |
|
Standard File Systems
|
FAT12/16 (SDSC), FAT32 (SDHC), exFAT (SDXC / SDUC) | — |
|
Operating Voltages
|
2.7V–3.6V (Standard) / 1.8V (UHS-I/II signal voltage) | — |
|
Mechanical Features
|
Write-Protect slide notch (left edge), 45-degree polarized corner keying | — |
|
Speed Class (Legacy C-Class)
|
— | Class 2 (2 MB/s), Class 4 (4 MB/s), Class 6 (6 MB/s), Class 10 (10 MB/s) |
|
UHS Speed Class (U-Class)
|
— | U1 (10 MB/s min sustained write), U3 (30 MB/s min sustained write) |
|
Video Speed Class (V-Class)
|
— | V6 (6 MB/s), V10 (10 MB/s), V30 (30 MB/s), V60 (60 MB/s), V90 (90 MB/s) |
|
App Performance Class A1
|
— | 10 MB/s sequential, Min 1,500 Read IOPS, Min 500 Write IOPS |
|
App Performance Class A2
|
— | 10 MB/s sequential, Min 4,000 Read IOPS, Min 2,000 Write IOPS (requires Command Queue & Host Cache) |
|
Guaranteed Metric
|
— | Minimum sustained sequential write speed on fragmented NAND (never peak burst speed) |