High on the list of gadget annoyances that make me want to scab my eyes out with a spork—just below cables and batteries—is the unfettered proliferation of memory cards. Even though they all fundamentally do the same thing—store data for handheld devices—they come in a million different sizes and shapes from almost as many companies, giving birth to retarded but necessary accessories. Anyone looking for proof of this can stop at the 80-in-1 card reader. Unfortunately, many of these dumb pieces of silicon and plastic aren't going extinct. As a consolation prize, here's an illustrated guide to all the ones you actually need to know.
CompactFlash is like the Big Mac of memory cards: It may be bulky, but no McRib is going to take its place any time soon. It long ago moved out of the consumer-oriented gadgets now primarily using SD card, but it's the go-to for pro digital SLR cameras because it's durable as hell, it can hold more data (up to 100GB) and transfer it a lot faster (up 66MB/s with the revision 3.0, though higher capacity cards don't yet reach that rate). All of that matters if you're shooting massive RAW photos at several frames a second in less-than-pampered conditions.
CompactFlash UDMA: The latest version of the CompactFlash spec, 4.0 adds support for the Ultra DMA 133 interface, pumping the maximum data transfer rate to 133MB/s. Looks the same as a regular CF card, but will have UDMA stamped on it. Enables longer burst shooting in the latest DSLRs, besides just sounding impressive. Of course, this parallel ATA interface is on the fast track to be slow balls, with a serial ATA based spec in the works that'll deliver 3-gigabit transfer rates, that is, nearly 400MB/s.
Secure Digital, better known as SD, is the memory card of the people. This sliver of plastic is the reigning king of storage in everyday gadgets, from digital cameras to the Nintendo Wii to non-iPod MP3 players to hell, my (admittedly fancy) alarm clock. Most new (non-Mac) notebooks come with an SD card slot, even if they don't support other cards. Its primary advantage over CompactFlash is smaller size—maybe the perfect memory card size, even. On the other hand, the standard version format is significantly slower, stores less data (the spec allows for up to 2GB, larger sizes exist) and is way more fragile. But damn if they aren't cheap.
Secure Digital High Capacity pretty much spells it out in the name—an extension of the SD format that allows for more storage (up to 32GB) and much faster write speeds (SanDisk's latest hit 30MB/s). Classes—2, 4 or 6—let you know what the card's minimum transfer speed is. The major catch is that while they look the same as a regular SD card, SDHCs won't work in older card readers. Most electronics are quietly swapping in readers that can support SDHC, and of course regular SD cards work wherever they physically fit.
MiniSD is, you guessed it, a smaller variant of the SD card format that's about a third of the size. And yes, there's an HC variant to bring its capacity past 2GB, just like SD to SDHC. Originally for the mobile phone space, it's basically been squeezed out by the even retardedly smaller microSD. Truth is, miniSD is all but extinct now. Fortunately it usually comes with an SD slot adapter, so old ones can just be used as standard SD cards.
MicroSD and its microSDHC step-up are ridiculously tiny, and though they're used in MP3 players and other gadgets, they now completely dominate removable storage on cellphones. They've got basically the same specs as the other SD and SDHC card flavors in theory, but they're not quite as speedy or obviously up to the same crazy capacities. Officially they are way too easy to lose.
MultiMediaCard is the format from which SD and its offspring descended. (Its looks should give it away.) There are a few variants, but since it's been displaced by its SD spawn, you probably won't run into them. They're even dissolving the MMC Association, if that tells you anything. The important thing to know is that if you come across one, it'll work in many—but not all—SD card readers.
Memory Stick and its 300 variations: Okay, it gets kind of ugly with Sony's essentially proprietary Memory Stick format. Once upon a time, Samsung, Sharp and possibly others had Memory Stick readers in certain portable electronics, but the days of non-Sony Memory Stick sightings are long gone. If I could punch the embodiment of Sony in the nuts for any single reason, it would likely be due to the continued existence of all 65,000 Memory Stick formats. Here's the rundown: The original Memory Stick, which is now obsolete, ran in sizes from 4MB to 128MB. There was also the Memory Stick Select, which was basically like two Memory Sticks crammed together with a switch to flip between the two.
Memory Stick PRO was the first legit sequel to the Memory Stick. It's faster, and theoretically holds up to 32GB, but has only been released in versions up to 4GB. PROs with more than 1GB of storage use a High Speed mode for faster transfers.
Memory Stick Duo was Sony's stab at getting small, shrinking its hot-dog proportioned Memory Stick into an SD-card sized package. Otherwise, it's just like a regular Memory Stick, stuck at 128MB and all. With an adapter it'll fit in regular Memory Stick readers too.
Memory Stick PRO Duo has the same SD-like form factor as the original Duo, but allows for much higher capacities and transfer speeds, about on par with SDHC cards. The highest capacity card is currently 16GB. Yes, there's still more Memory Stick where that came from.
Memory Stick PRO-HG Duo is the latest and largest mouthful of the Memory Sticks. Its big hurrah is that its 8-bit parallel interface gives you transfer speeds of up to 30MB/s, and the faster rates are majorly important for HD cameras. There is, unbelievably, another version, the PRO-HG Duo HX.
Memory Stick Micro aka M2 is the tiniest end of the line, comparable to a microSD card. Guess what it's used in? Sony Ericsson phones. Sadly, SanDisk participates in this farce of a format, along with the PRO-HG. The fattest available size is 16GB, which is notably pricier than its microSD cousin. Predictably, cards with heftier storage don't always play nice in older readers.
xD-Picture Cards are another BS format, created by second-tier camera makers Olympus and Fujifilm, that should just roll over and get smushed by the SD train. There, as always, a few different flavors—M, H, and M+—each one successively boosting capacity and/or speed but all fitting in the same small thin form. They're really only used in (you guessed it) Olympus and Fujifilm cameras—Kodak dabbled before hopping on the SD Express—and pathetically they only hold up to 2GB. Die already. Update: Okay, it does have one legit use—as a commenter has pointed out, it's descended from the extinct SmartMedia format, and provides easy access to a standard NAND flash chip, making it ideal for ROM-dumping for hackers.
SxS is another Sony-developed format, but it's geared toward pros and HD camcorders, with transfer speeds of 800Mb/s. It's available in sizes up to 32GB, but obscenely expensive—Sony sells the 16GB card, with one hour of recording time, for $1100. Conveniently, it uses the ExpressCard form factor, so it'll pop right in some notebooks.
P2 is another fancy ass, pricey pro-level card for camcorders, but it was developed by SD-pimpin' Panasonic. Not surprisingly, it was originally a bundle of SD cards in striped RAID array, but now it just uses core memory components in a RAID setup, contained in a ruggedized shell that fits into PC Card slots. It too goes up to 32GB, but the transfer rate is slower than SxS, at around 640Mbps. On the other hand, it's cheaper too, at $900 for a 16GB card. And that, friends, should just about do you, at least for a little while, or until Sony releases its next Memory Stick flavor of the week. Something you still wanna know? Send any questions about memory, Johnny Mnemonic or blackjack to firstname.lastname@example.org, with "Giz Explains" in the subject line. P.S. What other kinds of tech would you like to see an illustrated guide for?