SD Speed Classes vs. xD-Picture Card
Comparing 2 standards across 13 specifications. 13 key differences identified.
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).
xD-Picture Card ('eXtreme Digital') is a proprietary flash memory card format developed by Olympus and Fujifilm in 2002 (manufactured by Toshiba and Samsung). Measuring 20.0 × 25.0 × 1.7 mm with 18 surface pads, it utilized a controllerless architecture where the host camera directly managed the raw NAND flash silicon, before being discontinued in 2010 in favor of SDHC.
Specification Comparison Table
13 Parameters| Parameter / Spec | ||
|---|---|---|
|
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) | — |
|
Governing Manufacturers
|
— | Olympus Corporation & Fujifilm (manufactured by Toshiba/Samsung) |
|
Introduction Year
|
— | 2002 (superseded SmartMedia) |
|
Physical Dimensions
|
— | 20.0 mm × 25.0 mm × 1.7 mm (Weight: ~2.8 g) |
|
Pad Configuration
|
— | 18 gold-plated contact pads (bottom surface) |
|
Controller Architecture
|
— | Controllerless (Host camera CPU directly controls raw NAND flash) |
|
Variants & Capacities
|
— | Standard (16–512MB SLC), Type M (256MB–2GB MLC), Type H (256MB–2GB High Speed), Type M+ (up to 2GB) |
|
Nominal Operating Voltage
|
— | 3.3V nominal |