• About SD Association
  • Member Companies
    • Board Members
    • Executive Members
    • General Members
  • Contact Us
  • Fact Sheet
• Consumers
  • About SD Card Choices
    • Wireless LAN SD
  • About Compatibility with Host Devices
  • About Speed Class and Benefit
    • Speed Choices
    • Max Speed
    • Bus Speed
    • Optimize UHS Performance
  • About SDXC/microSDXC
    • Using SDXC
  • Usage Tip Videos
  • FAQs
• Developers
  • SD Standard Overview
    • Capacity (SD/SDHC/SDXC)
    • Bus Speed (Default Speed/ High Speed/ UHS)
    • Speed Class
    • Copyright Protection
    • Host Controllers
    • SDIO
    • iSDIO
    • ASSD
    • Embedded SD
    • Application Formats
    • SD Family
  • Start Using SD Standard
  • Use and Licensing
    • Non-Disclosure Agreement
    • SDA License Agreement
• Downloads
  • Simplifed Specifications
  • SD Card Formatter 4.0
    • SD Formatter 4.0 for Windows Download
    • SD Formatter 4.0 for Mac Download
• News & Events
  • Fact Sheet
  • Events
  • Association Press Release Archive
• Join the SD Association
  • Membership Benefits Comparison
  • FAQ
  • Membership Application
  • Glossary
• Members Site
  • Request Access to Members Area
  • Members Password Help
• HALA Site
• LAMS Site
• SDALA Site

Tools and Resources

Bus Speed

Because of the variety of high-performing and feature-rich devices in the market, there is a demand for higher performance SD memory cards. The SDA has introduced a higher bus interface with higher theoretical read and writing speed specifications for the SDHC standard and SDXC standard.

Bus Interface	Card Type	Bus Mark	Bus Speed	Spec Version
Normal Speed	SD, SDHC and SDXC	---	12.5MB/s	1.01
High Speed	SD, SDHC and SDXC	---	25MB/s	2.00
UHS-I	SDHC and SDXC		50MB/s (SDR50, DDR50) 104MB/s (SDR104)	3.01
UHS-II	SDHC and SDXC		156MB/s 312MB/s	4.00

*Maximum speed differs from the bus I/F speed. It varies depending upon the card performance. The average speed that a device writes to an SD memory card may vary depending upon the device and the operation it is performing. The speed may also depend on how other data is stored on the SD memory card.

Normal and high-speed cards can also be used with UHS-I host devices, but the high performance enabled by a UHS-I host device can only be achieved with a UHS-I memory card.