SDHC Memory

The Difference between SDHC and SD Memory Cards

            If you need a secure memory card that is 2GB or less in capacity, you want a SD Memory Card.  If you require a secure memory card that has a high capacity of 2GB or more, try a SDHC (Secure Digital High Capacity) Memory Card.  To estimate your capacity needs, you really should check the volume of data you wish to store in the memory card.  Storing still pictures as .jpg files, for example, of a 4GB SDHC memory card will allow 1,240 images of a picture resolution of 1,880 x 2,160 pixels. MPEG-2 Videos of 1 hour and 40 minutes can be stored on the same 4GB memory card, and it will playback at 5 Mbps for 30 fps.

            Alternately, MPEG-4 Video on a 4 GB SDHC Memory Card will store about 19 hours of video of a size of 320 x 240 pixels.  Playback at 384 Mbps will yield 15 fps.  If the memory card is used to store MP3 formatted music, the SDHC card will store a thousand songs, or about 68 hours of music.

            There are incompatibilities of SD and SDHC Memory Cards.  While they share most of the same standards, there are certain conditions that can cause issues.  The total memory capacity, addressed above,  is not the only issue.  Some devices that support SD Memory Cards do not even recognize SDHC Memory Cards.  Read your device specifications carefully.  If the device was manufactured after 2007, it should either be compatible or have cautions listed in its documentation about incompatibilities.  Check your device manufacturer’s website to be sure.  The specifications of SD cards has been revised.  Check to be sure your device accepts the latest 2.0 version of SD Memory Cards.

Specifications

            The SDHC Memory Card uses a standard that is an extension of the SD standard.  In addition to allowing a capacity higher than 2GB, the SDHC allows devices to format the memory card with the ‘FAT32' file directory and organization system.  This ‘FAT32' formatting system supports partitions within the card of 2 GB or greater.  SD Memory Cards cannot function with this type of formatting standard.  SDHC cards are available in capacities up to 32GB.

            The 2.0 revision to the SD memory standard accepts a different addressing scheme on ‘Fat32' organized high capacity memory cards.  The new standard allows devices to address the memory chip with either a byte and sector addressing.  Since the sector size can be different on the ‘FAT32' format, attempting to locate an address within the memory for a read or write can generate an error and cause your device to hang.  The SDHC trademark assures you that the memory card will be capable of both addressing patterns.  The user should make sure the device supports the new 2.0 standard.

            The SDHC Memory Cards are speed rated.  Depending on the product purchased, the following is the minimum sustained write speed:

            o          Class 2: Write Speed Minimum 2 Mbps

            o          Class 4: Write Speed Minimum 4 Mbps

            o          Class 6: Write Speed Minimum 6 Mbps

Low Price Memory Product Availability

            Low Price Memory (www.lowpricememory.co.uk) stocks many memory cards products, along with such products as SanDisk memory products, Sony Ericsson memory, Memory Stick Pro Duo products, SD Memory, SDHC Memory Cards, Compact Flash memory, Micro-SD memory, XD-Picture Cards, USB Memory, USB Pen Drives, Memory Card Readers, Camera Cases for digital cameras, Bluetooth Headsets, PC Memory in a number of formats, Laptop Memory for most portable computers, Sennheiser Headphones, and Camera Batteries.