A SD card will normally work in a SDHC device (possibly with lower performance). SD cards are in the following capacities 4,8,16,32,64,128,256 512MB and 1GB, 2GB only. Currently mainly 2GB SD cards are being sold. A SDHC card will not work in a SD device such as a camera or reader.
http://www.integralmemory.com/faq/cards-what-difference-between-sdhc-and-sd-cards
1 Select Internal Memory Card Reader and look for the Speed entry. 2  Select Card Reader from the Hardware section (for Macs that use the PCIe bus to communicate with the SD card slot). 3  Look for the Link Speed entry. 4  Computers that use the PCIe bus express their speed as GT/s.
https://support.apple.com/en-us/HT204384
SDHC is the same physical size and shape as standard SD but meets the new SD specification of version 2.0. If the SD card is 4GB or above, it is classed as a SDHC card. Currently, SDHC specifications allow for memory cards of a capacity between 4GB and 32GB. SDA (SD Card Association) has also established a Speed Class rating (Class 2, 4, 6 and 10) for the standardisation of data transfer speeds (compulsory for SDHC cards): 1  CLASS 2 - a guaranteed minimum write speed of 2MB/s or higher*.
http://www.integralmemory.com/faq/cards-what-difference-between-sdhc-and-sd-cards
The SDHC card is compliant with the SD speed class rating specification created by the SD association which introduced a new speed classification according to the application: * Do take note that Class 2 SDHC Card is generally cheaper than Class 4 SDHC due to the speed difference. * You also need to take note on the compability issues while purchase the SDHC Card: * SDHC Host devices can use SD (up to 2GB) and SDHC (4GB and more) Memory Cards.
http://www.ebay.com/gds/What-is-SDHC-Card-Whats-the-difference-with-normal-SD-/10000000003211001/g.html
1 or. 2  Select USB from the hardware section (for Macs that use the USB bus to communicate with the SD card slot). 3  Select Internal Memory Card Reader and look for the Speed entry. 4  Select Card Reader from the Hardware section (for Macs that use the PCIe bus to communicate with the SD card slot).
https://support.apple.com/en-us/HT204384
Determine the maximum speed of your Mac using the System Profiler: 1  Choose About this Mac from the Apple () menu. 2  Click More Info. 3  or. 4  Select USB from the hardware section (for Macs that use the USB bus to communicate with the SD card slot).
https://support.apple.com/en-us/HT204384
* SD Host devices can use only SD Memory Card (up to 2GB). Therefore SDHC cards are never compatible with SD Host products. To check whether a device is SDHC compatible, customers need to check the manufacturer's documentation. Only the most up to date devices will be SDHC compatible.
http://www.ebay.com/gds/What-is-SDHC-Card-Whats-the-difference-with-normal-SD-/10000000003211001/g.html
Secure Digital (SD) is a non-volatile memory card format developed by the SD Card Association (SDA) for use in portable devices. The standard was introduced in August 1999 as an improvement over MultiMediaCards (MMC), and has become the de facto industry standard.
https://en.wikipedia.org/wiki/Secure_Digital
SDHC stands for High Capacity SD Memory Card. SD Card Association (SDA) introduces this new-generation specification (Ver. 2.0) SD card in May, 2006, which has a capacity ranging from 2GB to 32GB. SDHC main features is its High Capacity(2GB to 32GB).
http://www.ebay.com/gds/What-is-SDHC-Card-Whats-the-difference-with-normal-SD-/10000000003211001/g.html
1 Click More Info. 2  or. 3  Select USB from the hardware section (for Macs that use the USB bus to communicate with the SD card slot). 4  Select Internal Memory Card Reader and look for the Speed entry. 5  Select Card Reader from the Hardware section (for Macs that use the PCIe bus to communicate with the SD card slot).
https://support.apple.com/en-us/HT204384
what is a sdhc card
An SDHC card is a High Capacity SD memory card. A SDHC card is a High Capacity SD Memory Card.