SD (Secure Digital) and SDXC (Secure Digital Extended Capacity) memory cards are non-volatile storage devices used in portable devices such as digital cameras, phones, and handheld game consoles. Both types of cards allow you to store photos, videos, music, documents, and other files on flash memory.
SD cards have been around since 1999, originally created by Panasonic, SanDisk and Toshiba. SDXC is a newer specification introduced in 2009 to support cards with capacities larger than 32GB. While both use flash memory, there are some key differences between SD and SDXC in terms of physical design, storage capacity, speed, file system, and device compatibility.
Origins and History
The SD card was first introduced in 1999 as a joint effort between SanDisk, Panasonic (Matsushita Electric) and Toshiba as an improvement over MultiMediaCards (MMCs). It was designed to offer higher capacity storage in a smaller form factor. The SD Association was formed to promote and develop the format.
According to the SD Association, the SDXC (eXtended Capacity) format was unveiled in January 2009 at the Consumer Electronics Show. It was designed to offer higher capacity cards starting from a minimum of 64GB up to 2TB, compared to a maximum of 32GB for standard SD cards at the time. The SDXC specification also defined faster minimum speed requirements than previous formats.
Sources:
https://en.wikipedia.org/wiki/SD_card
https://www.digitalcameraworld.com/features/flash-back-the-history-of-the-sd-card-and-why-we-think-it-deserves-more-love
Physical Differences
SD and SDXC cards have some notable physical differences in terms of their size, weight, and shape:
Size: SD cards are 32 x 24 x 2.1 mm, whereas SDXC cards are slightly larger at 24 x 32 x 2.1 mm [1]. The SDXC’s extra width allows it to accommodate more pins and contacts.
Weight: SD cards weigh approximately 2g, while SDXC cards are lighter at around 1.5g. The lighter weight comes from the newer manufacturing process used for SDXC cards.
Shape: Both SD and SDXC cards have a rectangular shape. However, the location of the write-protection switch differs. On SD cards, it is on the side, while on SDXC cards, it is on the front [2].
So in summary, SDXC cards are slightly larger, lighter, and have a differently positioned write-protection switch compared to SD cards.
Storage Capacity
One of the key differences between SD and SDXC cards is the maximum storage capacity. According to the SD Association, SD cards are available in capacities up to 2GB, while SDXC cards can go up to 2TB.
The SD standard originally supported cards up to 2GB. The SDHC standard increased the maximum capacity to 32GB. Then in 2009, the SDXC standard was introduced to support cards up to 2TB. So SDXC cards have a much higher maximum storage capacity compared to original SD cards.
In practical terms, if you need a memory card greater than 32GB, you’ll need an SDXC card. SD cards top out at 2GB and SDHC at 32GB. For high capacity storage needs like 4K video recording, SDXC is required.
Speed
SD and SDXC cards differ significantly when it comes to read and write speeds. SD cards typically have maximum read speeds ranging from 10-25 MB/s and maximum write speeds of 2-10 MB/s. In contrast, SDXC cards are much faster – they support Ultra High Speed bus interfaces and command protocols, allowing for minimum sustained write speeds of 10 MB/s and maximum read speeds over 90 MB/s.
SDXC cards use speed classes like UHS Speed Class 1, Class 3, and Class 10 to indicate their minimum write performance. For example, UHS Speed Class 1 cards offer minimum write speeds of 10 MB/s, while UHS Speed Class 3 cards can write at a minimum of 30 MB/s. Higher speed classes correspond to faster performance. This speed class rating makes it easy to identify the sustained write speed of SDXC cards.
Additionally, SDXC cards will be labeled with maximum read speeds. For instance, SanDisk Extreme Pro SDXC cards have maximum read speeds up to 300 MB/s (Kingston). The read speed is almost always faster than the write speed. While SD cards top out around 25 MB/s read speeds, SDXC cards can reach over 90 MB/s for reading data.
In summary, the advanced bus interfaces and protocols of SDXC allow for much faster read and write speeds compared to standard SD cards. The speed classes make it simple to choose an SDXC card with sufficient write performance for your needs.
File System
The SD and SDXC cards use different file systems. SD cards commonly use the FAT32 file system, while SDXC cards use the exFAT file system.
FAT32 has been around since the days of Windows 95. It stands for File Allocation Table 32-bit. FAT32 supports files up to 4GB in size and volumes up to 2TB. It is compatible with most devices. However, its age means it lacks some more advanced features of newer file systems.
exFAT, Extended File Allocation Table, was introduced in 2006. It supports larger maximum file sizes up to 16EB and larger maximum volume sizes up to 128PB. It also has faster formatting times and better performance with large files compared to FAT32. However, exFAT has less compatibility with older devices than FAT32.
In summary, SD cards usually use the older but more compatible FAT32 file system, while SDXC cards use the newer exFAT system that supports larger files and volumes but has less compatibility with older devices. This is a key technical difference between the two formats.
Source: https://www.howtogeek.com/235596/whats-the-difference-between-fat32-exfat-and-ntfs/
Compatibility
SD cards are backward compatible, meaning SDXC cards will work in SDHC and SD devices, while SDHC cards will work in SD devices. However, the reverse is not true – SDHC cards will not work in SDXC devices and SD cards will not work in SDHC or SDXC devices.
Specifically:
- SDXC cards can be used in SDXC and SDUC host devices, as well as SDHC, SD, and regular host devices.
- SDHC cards can be used in SDHC host devices, as well as SD and regular host devices.
- SD cards can only be used in SD and regular host devices.
So in summary, SDXC has the widest compatibility, followed by SDHC, and SD has the most limited compatibility. When purchasing a card, it’s important to check which format your device supports to ensure compatibility.
Uses
SD cards are typically used in digital cameras, camcorders, and older mobile phones that have SD card slots. The storage capacity of SD cards ranges from 1 GB to 2 TB, making them well-suited for storing photos, videos, music, documents, and other media files on devices (Kingston).
SDXC cards are primarily used in newer digital cameras, camcorders, and mobile devices that support the exFAT file system. Their higher storage capacities of 64 GB to 2 TB make them ideal for shooting high resolution photos and high definition video. SDXC cards are also commonly used in drones, handheld gaming systems, laptops, and 4K TV recording boxes (TechTarget).
Pricing
SD cards have become much more affordable over time. According to 7dayshop, the cost per gigabyte for SD cards has fallen 100 times in the past 10 years. In 2006, an SD card cost around £27.50 per gigabyte. Nowadays, high capacity SDXC cards can be purchased for as little as £0.27 per gigabyte.
When comparing SD and SDXC cards, SDXC tends to be more expensive per gigabyte. According to Consumer Reports, this pricing difference is largely due to the higher capacities available with SDXC. While SD supports up to 2GB, SDXC supports capacities starting from 32GB up to 2TB. The higher capacity SDXC cards utilize more sophisticated memory chips that are pricier to manufacture. However, the cost per gigabyte still trends downward as capacity increases for both card types.
Summary
To briefly summarize the key differences between SD and SDXC memory cards:
SD cards have a maximum capacity of 2GB, while SDXC cards can store up to 2TB.
SDXC uses the more modern exFAT file system, while SD uses the outdated FAT32 system.
SDXC cards have faster minimum write speeds and are better suited for recording high-resolution photos and video.
SDXC works with newer devices, but may not be compatible with some older devices that only support SD and SDHC.
SDXC cards are more expensive than SD cards for an equivalent storage amount.
In summary, SDXC offers far greater storage capacity, better performance, and more modern compatibility compared to standard SD cards.