CFexpress vs. SD Speed Classes
Comparing 2 standards across 13 specifications. 13 key differences identified.
CFexpress is an ultra-high-speed removable solid-state storage media standard developed by the CompactFlash Association (CFA). Built directly on the PCI Express (PCIe Gen 3/Gen 4) physical bus and NVM Express (NVMe) command set, it is the dominant storage medium for high-end professional digital cinema, mirrorless photography, and broadcast video.
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) | — |
|
Underlying Storage Architecture
|
PCI Express (PCIe Gen 3 / Gen 4 / Gen 5) + NVM Express (NVMe v1.3/1.4) | — |
|
Type A Dimensions & Bus
|
20.0 × 28.0 × 2.8 mm | 1-lane PCIe (1 GB/s PCIe 3.0 / 2 GB/s PCIe 4.0) | — |
|
Type B Dimensions & Bus
|
38.5 × 29.6 × 3.8 mm | 2-lane PCIe (2 GB/s PCIe 3.0 / 4 GB/s PCIe 4.0) | — |
|
Type C Dimensions & Bus
|
54.0 × 72.0 × 4.4 mm | 4-lane PCIe (4 GB/s PCIe 3.0 / 8 GB/s PCIe 4.0) | — |
|
Type B XQD Compatibility
|
Physically identical exterior shell to Sony XQD (host backward-compatible via firmware) | — |
|
Operating Power Tiers
|
Up to 1.7W (Type A) / Up to 3.0W (Type B) / Up to 6.0W (Type C) | — |
|
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) |