Unlike the dark ages of flash memory, consumers today are lucky to have a few, well-established formats from which to get their storage fix. But
like the floppy disk, many portable storage formats have been phased out over time due to technical limitations and lack of consumer support (remember Olympus's
xD format?). Today, most devices tend to use some form of
Secure Digital (SD),
Compact Flash (CF) or, if you're a Sony geek,
Memory Stick. But physical appearances aside, time has done little to truly separate one standard from the next. Read speeds, write speeds and class numbers are thrown about like badges of honor, but what do any of these things really mean? Rest assured, there are differences. It pays to know what each format has to offer, and more importantly, the which format has what it takes to outlast the competition.
Compact Flash is the oldest of the standards in use today, and the format curmudgeonly tech geeks might be most familiar with. Introduced by SanDisk in 1994, CF cards were originally designed to be compliant with
PCMCIA, the popular expansion port most commonly found in laptops. The advantage was that these small, CF cards could act as tiny, removable hard drives -- much like how the
iPod Mini was designed, for example. With full ATA support, CF cards could appear as another hard drive to the host OS, bringing superior transfer speeds and reliability when compared to other flash solutions.
By dividing the speed rating of a CF card by 8, you can quickly determine the potential write speed of the card. A CF card rated at 300x, for example, can offer theoretical write speeds of at least 45Mb/s. And while other technologies have begun to catch up, this once proved especially advantageous during the earlier days of USB, where SD and Memory Sticks offered far slower transfers. But unlike other technologies, current CF cards max out at 128GB. However, a
newer CF spec announced this year says the theoretical capacity of a card can now reach a staggering 144 Petabytes -- good news for the photographers and filmmakers who still rely on these cards each day. Yet, all these features come at a price, and a 16GB CF card can often be double or triple the price of a smiler SD offering.
But as great as CF cards can be, they're rather large, and not as portable as SanDisk's later invention, Secure Digital. Developed alongside Panasonic and Toshiba with mobile platforms in mind, the "Secure" portion actually referred to the inclusion of DRM options in earlier products -- quickly deemed less popular than previously thought. Today's SD cards are divided into
Class 2, 4 and 6 branded cards, with
Class 10 cards announced last year. These numbers are much easier to decipher than the speed rating numbers of CF, and represent 2Mb/s, 4Mb/s, 6Mb/s or 10Mb/s minimum write speeds.
But unlike their Compact Flash counterparts, SD cards lack a similar ATA backend and aren't commonly used as hard drive substitutes in devices or PCs. However, their size and relatively fast speed makes them a perfect fit for almost every portable device on the market today, from cameras to phones and even gaming consoles. Such proliferation has also made them the cheapest form of storage on the market. And although, the current SDHC spec only allows cards up to 32GB in size, a
newer SDXC spec should expand that to 2TB.
To round things off, there's Sony's Memory Stick. Released about a year before the launch of SD, this format is well known to anyone who has ever owned a Sony product, as it's generally the only form of removable storage supported by the company's devices. Historically, storage space has been a problem with Memory Stick products, and higher-capacity models are often far more expensive than their SD or CF counterparts. Combined with the company's smaller user base, Memory Sticks can often be the priciest storage on the market. However, in terms of speed, Sony's Memory Stick places somewhere between its CF and SD counterparts. The company's Memory Stick Micro line, for example, can reach maximum transfer speeds of 20Mb/s, while the high capacity XC line is said to reach 60MB/s with
up to 2TB of storage space possible.
In terms of speed, it's no wonder that Compact Flash cards are still used to this day. Despite their larger size, superior write speeds have made these cards particularly attractive for those shooting HD video or similar high quality content. However, SD's size and price has made it the preferred format for almost every mobile product on the market. And Sony? Well, their cards are still expensive, and still proprietary. But given the choice, at least you can determine which one is best for you.
