Introduction

• SD cards were introduced in 2000. SDHC cards were introduced in 2006.
  
  

Size

• SD cards can store up to 4 gigabytes (GB) of data. SDHC cards can store up to 32 GB.
  
  

Physical Specifications

• SD and SDHC cards are the same size: Regular SD and SDHC cards are 32 mm x 24 mm x 2.1 mm. Mini and micro cards are smaller, but are identically sized for both SD and SDHC cards.
  
  

Function

• Both the SD and SDHC cards use the same basic method for storing data--writing information using tiny logic gates--but use different ways of organizing the data. SD uses byte addressing and SDHC uses sector addressing, which allows for more storage.
  
  

Compatibility

• SD cards work in any device that accepts SDHC cards. SDHC devices need a firmware upgrade to accept SD cards.