Getting the most out of your PDA: Storage

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Since PDAs don’t have a lot of storage built in, there are a number of storage options for PDA users. Most of them come in the form of removable memory cards, like the CF and SD cards I mentioned previously. The storage on a PDA is a form of read-only memory (ROM) that is nonvolatile, meaning that it doesn’t lose its information when it loses power, like your computer’s random access memory (RAM) does.

The ROM chips used in PDAs are called flash memory. Unlike older ROM chips, their information can be rewritten, or “flashed,” by the user. There are two types of flash memory used today: NOR (Not OR) and NAND (Not AND). NOR and NAND are types of Boolean logic used to create logic gates on chips. NOR flash memory can store and execute software. This is the type of flash memory used in PDAs, cell phones, and digital cameras. The device’s software resides and operates in NOR memory; this ability is known as execute in place (XIP).

NAND memory stores data but does not execute programs. Software stored in NAND memory must first be copied into NOR flash memory or RAM. NAND flash memory is faster, cheaper, and more durable than NOR, and can be written up to one million times. The flash memory in most removable card media is NAND flash memory.

Storage media come in a wide variety of adapter cards. Installing a card is as simple as inserting it into the proper adapter slot on your PDA, which will recognize the storage card and allow you to format it as well as copy files to it. Yam can leave the storage card in for as long as you need, or remove it for convenient storage. You can also purchase card readers that hook up to your computer using the USB port so that you can copy files from your PDA to your PC with the storage card.

CF cards range in price from $10 (32MB) to over $450 (2GB). SD cards range from $15 (32MB) to over $270 (512^ffl). Multimedia cards (MMCs) and Memory Sticks (MSs) have a similar price range. To determine which type of card your PDA supports, consult the PDAf¡¯s user manual or product information. In some cases, the card type is printed on the PDA’s card slot. You can also visit the manufacturer’s Web site to find out which card your PDA supports.

Compact Flash

CF was introduced by San Disk Inc. in 1994. It is very popular among manufacturers of everything from cameras to PDAs. Because CF cards use the same electrical interface as PCMCIA cards, but have fewer pins, they can be used in PCMCIA slots with an adapter.

The newest type of CF card, Compact Flash Type II (fc\F2), is slightly thicker than the original cards, which allows more electronics to be included in each card. Some manufacturers, including IBM, have begun to produce micro-miniature hard disks enclosed in CF2 cards.

Because both cards use the same electrical interface, a CFl card fits into a CF2 device and still operates, but a CF2 card is too thick to be inserted into a CF1 slot.

Secure Digital

This type of card is becoming very popular, with many PDA manufacturers opting to adopt SD cards over CF cards in their newer models. Because SD cards are quicker than other memory cards, they are popular as storage media.

SD cards are similar to MMCs, but thicker. SD card readers accept MMCs, but not vice versa. In 2003, a newer Mini SD card was introduced which is less than 40 percent of the size of the original SD card, but fully compatible. SD card readers accept Mini SD cards. Full-sized SD cards are available with capacities of up to 1GB, while Mini SD cards are available up to 256MB.

PCMCIA

Some PDAs have PCMCIA card slots that support PC cards, but these are not nearly as common as SD or CF cards. PC cards are 16-bit devices, more often seen on laptops than PDAs. PC cards are one way to extend the functionality of laptops. The most common PC cards are Type II cards, which are 5.0mm thick and used for LAN adapters and storage in laptops.

There is also a Type IB PC card that is 10.5mm thick and used for wireless adapters, hard disks, and other devices. Type II cards will work in Type IB adapters, but not vice versa. Toshiba has proposed a Type IV card, but it hasn’t been accepted as a standard yet.

Memory Stick

The MS is a flash memory card produced by Sony and used in many of its products. MSs are smaller than a stick of gum and are also used in IO devices, such as mini-cameras for some Sony PDAs. MSs are not widely used outside of Sony’s products.

Multimedia Cards

Multimedia cards, or MMCs, are widely used and compatible with many SD card readers. They’re supported by many device manufacturers and are often used for delivery of PDA software. Multimedia cards use either NOR or NAND flash memory, depending on the intended use of the card. NAND cards are the choice for memory expansion.

There is also a secure version of the MMC that protects copyrighted material, and can be used in e-commerce transactions.

Micro drive

Micro drives are microminiaturized hard disks, some less than the diameter of a nickel that you can use for storage in portable devices. Compared to flash cards, they are faster and can store more information. These smaller drives conserve power compared to larger hard drives, although they still have the disadvantage of being mechanical, rather than solid state, and are more susceptible to damage and mechanical failure as a result. Micro drives also produce heat, another disadvantage compared to solid state flash memory.