- What's Flash Memory?
- NOR/NAND Flash Memory
- Memory cards: Form defines function
- What is CompactFlash?
- What is Microdrive?
- What is Memory Stick?
- What is SD/MMC/RS-MMC/MMC Micro/miniSD/MicroSD?
- What is Smart Media?
- What is XD-Picture card?
- Flash Drives with everything
- What are USB keys?
- What are ExpressCards?
There are dozens of memory card formats and making the right choice when buying one can make the difference between spending a fortune on a chunk of plastic or buying the right tool for the job. This guide will introduce you to the different memory card formats on the market and give you a buyer's overview of what to look out for when purchasing memory cards.
What's Flash Memory?
Flash Memory lies at the heart of every memory card -- and every USB Key, iPod Nano and a number of other storage-based devices. Unlike the memory in your PC, which is erased every time the power is switched off, Flash Memory is non-volatile, meaning it retains information without an external power source. Originally devised by Japanese researchers working for Toshiba, Flash Memory has become the storage medium of choice for memory cards because it's relatively cheap to produce, quite shock resistant and able to be written to and from millions of times before the card expires.
NOR/NAND Flash Memory
NOR and NAND are logic gates that define how an action will be performed. Without going into the basics of logic programming, the only thing you need to know about NOR and NAND from a consumer viewpoint is that pretty much all new Flash Memory is built as NAND Flash Memory. The earliest flash memory was NOR based, but NAND has overtaken it, largely due to the reliability of the media. NOR memory typically won't last beyond 100,000 write/erase cycles (and sometimes much less), while NAND Memory can manage up to a million such cycles.
Memory cards: Form defines function
The most common use of memory cards in the consumer world today is as storage media for digital cameras, often referred to as digital film. There are a number of different formats and vendors that will talk up the advantages of their format (because they want your money), but for the most part, your choice of card isn't all that open ended. What you can use is largely determined by the devices you already have, or those you plan to buy. While there's some cross-compatibility between certain formats -- SD-compatible readers can normally handle MMC, for example -- for the most part if your camera takes Memory Stick, for example, then that's what you'll end up using.
While there are plenty of formats out there, it's thankfully not that difficult to set yourself up to be able to read cards from anyone's camera/PDA/music player, as multi-card readers are cheaply available. Many mid-range inkjet printers now come with embedded card readers capable of reading at least SD/MMC/CompactFlash and Memory Stick, although few support the smaller miniaturised card formats, which are largely intended for use in small portable devices such as mobile phones.