How are SDHC Cards and SD Cards Difference

What’s the Difference Between a SDHC Card and an SD Card?

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What is SDHC?

Secure Digital High Capacity (SDHC) devices are flash memory cards with a minimum capacity of 4GB (gigabytes) of storage capacity. SDHC cards are a removable storage solution for compatible digital devices including digital MP3 players, cameras, camcorders, PDAs and more. SDHC cards are the same size as an ordinary SD Card and were developed to meet the demand for more storage capacity and greater performance characteristics. SDHC cards are designed for devices that are compatible with the SD 2.0 specification. Products designed exclusively to support previous SD specifications 1.0 and 1.1 will not be able to use SDHC cards. Check your device manual for compatibility.

  • Remember, if your device accepts SDHC cards, it is backwards compatible with standard Secure Digital (SD) cards.

Why Use an SDHC Card?

The growing demand for high-capacity flash memory is in part due to the increasing use of high-definition video and high-resolution digital photography. SDHC cards meet the challenge of these demanding products not only by providing ample storage but also by introducing a new Data Transfer Speed (DTS). There are different classes of DTS.


  1. Class 2: minimum sustained DTS of 2MB/sec (13x Speed)
  2. Class 4: minimum sustained DTS of 4MB/sec (26x Speed)
  3. Class 6: minimum sustained DTS of 6MB/sec (40x Speed)

Besides Size, What the Difference Between an SD and an SDHC Card?

SD memory cards do not start writing at their maximum speed. They need to build up to it. SDHC cards per class specification begin writing at their fastest DTS. So, a card in the SD format (e.g., digital video camera) will start writing the image or data to the card at 0MB/sec and then work up to the top operating speed and then slow down again to 0MB/sec as it finishes wrting the data. This makes the optimum writing speed more than optimum.

In the SDHC format, which has a guaranteed minimum write speed of say 6MB/Sec (40x Speed) will start at this speed and may in fact have a higher top speed. For instance, a Class 6 card having a minimum sustained write speed of 6MB/Sec – 40x Speed, may achieve a top speed of 20MB/Sec at 133x Speed.

Secure Digital was forced to create a new specification for SDHC cards when the previous specification topped out at a capacity of 2GB. The new 2.0 specification allows SDHC cards to reach a maximum capacity of 32GB.

Before purchasing and SD or SDHC memory card, be sure of the compatibility of your device.

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