CompactFlash vs. SD Speed Classes
Comparing 2 standards across 14 specifications. 14 key differences identified.
CompactFlash (CF) is the pioneering solid-state removable memory card standard introduced by SanDisk in 1994 and maintained by the CompactFlash Association (CFA). Based on a 50-pin Parallel ATA (PATA / IDE) interface, it dominated professional DSLR photography and industrial computing for two decades, scaling through CF+ specifications up to UDMA 7 (167 MB/s).
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
14 Parameters| Parameter / Spec | ||
|---|---|---|
|
Governing Body
|
CompactFlash Association (CFA) | — |
|
Introduction Year
|
1994 (SanDisk) | — |
|
Physical Dimensions
|
36.4 mm × 42.8 mm × 3.3 mm (Type I) / 5.0 mm (Type II) | — |
|
Physical Connector Form Factor
|
50-pin female socket receptacle (2 rows of 25 pins on 1.27 mm pitch) | — |
|
Interface Protocol
|
Parallel ATA (PATA) / True IDE Mode / PCMCIA Memory Mode | — |
|
Max Bus Speed Tier
|
UDMA 7 (167 MB/s @ 133 MHz PATA clock in CF 6.0) | — |
|
Operating Voltages
|
Dual voltage: 3.3V (low power) or 5.0V (legacy standard) | — |
|
Video Performance Guarantee
|
VPG-20 (20 MB/s) / VPG-65 (65 MB/s sustained write for Full HD / 4K) | — |
|
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) |