More Memory in a Flash

You use your new digital camera or PDA extensively for some time, until you realize it doesn’t have the space left to store additional photographs or data. What do you do in such a case? That’s where Flash memory comes in. Most devices like these have the provision to add extra memory. Unfortunately, there are so many types of memory devices that you can easily get confused. PCQuest tells you of the different types of memory devices available. 

Electronic memory comes in a variety of forms to serve a variety of purposes. Initially, there were two types of memory:

RAM and ROM. RAM is the SDRAM/RDRAM variety of memory found in computers. It’s volatile, meaning all data is lost when the power is turned off. ROM, on the other hand, is non-volatile and, therefore, contains fixed program codes.

However, once the data is written, it cannot be altered. Developments in ROM resulted in EEPROM (Electrically Erasable ROM) wherein you could reprogram the memory chip using electrical signals. Finally, came Flash memory, which is not only non-volatile like EEPROM, but also doesn’t need separate complex equipment to generate the electrical signals for reprogramming it. You can store data in it just as you do in a hard disk. Flash memory is primarily used for easy and fast information storage in devices like digital cameras, handheld PCs, digital audio players, laptops and other portable handheld devices. The BIOS of most computers nowadays is also made of Flash memory. 

Flash memory is solid-state, meaning it has no moving parts like the magnetic rotating disks found in hard-disk drives, which are subject to mechanical problems. It’s more rugged and reliable, having a shock rating of 1000-2000 Gs, equivalent to a 10 feet drop on concrete. Mechanical disk drives have a rating of 100-200 Gs. Flash devices can also operate in extended temperature range of -40C to +85C compared with a range of +5C to +55C. They also consume lesser power. In fact, it’s less than five percent of the power required to operate portable disk drives. It can work with systems working with two AA batteries, making it a good choice for digital devices. They’re also highly portable owing to their small size and

lightweight–you can easily carry them in a shirt pocket.

Flash memory also has its own limitations. First, the cost per megabyte of storage exceeds mechanical drives by orders of magnitude. They are, in fact, more expensive than SDRAM. Second, they haven’t reached anywhere near magnetic storage in terms of capacities. Today, Flash memory capacities range from a few MB up to 4 GB. 

Types of Flash memory 



Five major flash memory formats are predominant in the market today–Compact Flash, Memory Stick, Multimedia Card, Secure Digital and Smart Media. 

These support different standards and also vary in size, capacity, etc. Due to this, most are also incompatible with each other. So if you have two gadgets supporting two different memory formats you have to buy separate memory devices for them.

Smart Media: Also known as SSFDC (Solid State Floppy Disk Card), Smart Media was originally developed by Toshiba.

It’s larger than the other memory devices, but smaller than the PCMCIA card-based memory devices. Smart Media cards are very simple in design, with the memory chip directly connected to the card, and have no controller circuitry on it. 

Compact Flash (CF):

Another widely used format that’s almost the same size as Smart Media cards, but thicker. These come in two varieties: Type I and Type II. This format also has I/O specifications, so you have modems, wired and wireless networking cards and other interfaces for CF slots. CF data storage cards are also available using magnetic disk like the IBM Microdrive, which is actually a tiny magnetic disk storage device packed inside a CF card. This looks and works like a normal CF card, but is slightly heavier.

Memory Stick: This format was developed by Sony and its size is small enough for the smallest of devices. Many I/O devices, such as those with Bluetooth enabled, GPS, digital cameras and handheld PCs, support the Memory Stick.

MultiMedia Cards (MMC): Initially targeted at the cellphone and pager market, MMC is now available for digital cameras, handheld PCs and several other portable devices. They are the smallest format available and don’t have any I/O specifications, so no external devices like cameras, GPS or networking devices are available for MMC slots.

Secure Digital (SD): Co-developed by Panasonic, SD is the latest and much talked about memory-card format. It is the same size as MultiMedia card, but at 2 mm it is slightly thicker. The format was initially intended to protect the music industry by incorporating copy protection and digital rights management sche-mes, but the specification was cracked soon after its release and the security readiness of the card is a moot point now. It is available in sizes up to 512 MB and I/O devices for it are emerging.

Other devices: Apart from these, PCMCIA memory cards are also available, which are larger in size and mostly used as solid-state disks on laptops. Another type of Flash memory is the USB key drive, which enables the easy transfer of files from one computer to the other, but cannot be used with many other digital devices because the devices do not support data transfer directly to a USB drive. USB drives are available in sizes up to 128 MB. 

Which one?



With so many formats, your choice depends mainly on the type of slot available in your digital device. Most digital devices nowadays support more than one card. In the long run, three formats–Compact Flash, Memory Stick and Secure Digital–might dominate the market. Compact Flash offers the highest capacities and is the most widely compatible format with a whole array of products supporting it. Memory Stick is predominantly used in Sony products, but is also supported by products from other vendors. SD cards are the latest entrants, and one of the reasons for their growing popularity is that they can also take multimedia cards. Plus, with the format’s emerging I/O specifications, many external network devices, cameras and modems connecting to the SD slot will start coming up. MultiMedia Card, though slightly thinner than SD, may lose its shine to SD, as many manufacturers are building SD slots instead of MMC slots. Smart Media cards are the slimmest, but that only limits its memory capacity and also there are no I/O capabilities with this format.

If you are still caught in a situation where you have a different card than supported by your device, multi-card reader/writers are available. They take a variety of card formats as input and on the output you can have any interface like the USB, FireWire, parallel port, IDE (so the card behaves like a normal IDE disk, which can be used for booting also) and PCMCIA. Now you can buy any card and use an adapter to connect it to your gadget or your computer.

Anoop Mangla