CFast vs. SD Speed Classes
Comparing 2 standards across 13 specifications. 13 key differences identified.
CFast is a high-speed solid-state memory card standard developed by the CompactFlash Association (CFA) based on the Serial ATA (SATA) bus. Introduced with CFast 1.0 (SATA-II 3 Gbps) and refined in CFast 2.0 (SATA-III 6 Gbps), it delivers data throughput up to 550–600 MB/s in a rugged 24-pin form factor, widely adopted in professional cinema cameras (ARRI, Blackmagic, Canon).
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
|
CompactFlash Association (CFA) | — |
|
Physical Dimensions
|
36.4 mm × 42.8 mm × 3.6 mm | — |
|
Bus Interface / Protocol
|
Serial ATA (SATA 3.0 / 6 Gbps in CFast 2.0) | — |
|
Physical Connector Form Factor
|
24-pin keyed interface (7-pin SATA signal + 17-pin SATA power & control) | — |
|
Peak Data Throughput
|
Up to 550–600 MB/s (SATA-III physical ceiling) | — |
|
Nominal Operating Voltage
|
3.3V nominal | — |
|
Video Performance Guarantee
|
VPG-130 (130 MB/s minimum sustained write for 4K ProRes/RAW) | — |
|
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) |