HOW TO: Choosing a PDA Based on Memory Storage Type

by Reads (10,313)

The world of PDAs can be somewhat overwhelming and confusing, you have to choose between Palm OS, Pocket PC or Linux and then determine which manufacturer you trust that makes those devices. The decision making doesn’t stop there, one major factor that should be considered is which external memory Storage capacity a PDA uses. What’s better, CompactFlash (CF Type I or CF Type II), Secure Digital (SD), Memory Stick, or MultiMedia Card (MMC). What, you might ask, is even the difference between these formats and why have we arrived today at a point where the storage mediums are so varied. To the average consumer, it’s rather annoying. In this article I will give an overview of each type of memory and what the strengths and weaknesses are of each, and then recommend which type of memory expansion to look for in a PDA device.

Flash Memory – What is it?

One thing we can say about all these memory types is that they are all a form of flash memory. Flash memory is a technology invented in the 1980s by Toshiba. Flash memory allows for data to be saved even when the memory’s device is disconnected from its power source — a fact we take for granted today of course since we now rely on flash storage for a variety of consumer and industrial devices such as the following:

– Notebook computers, Personal Digital Assistants (PDAs), MP3 players, Digital Cameras, Cell Phones, Pagers, Security Systems, Military Systems, Medical Products.

What advantages does flash memory have?

Flash memory has several key features that make it perfect for storage in todays electronic computer devices. Flash cards have no moving parts and are thereby not subject to the mechanical failure issues of hard drives, since no moving parts are present the noise level of running a flash card is literally zero decibels. Flash cards also have high temperature and shock endurance, so although your PDA won’t survive a drop to the floor then chances are your memory will. The data reliability of flash memory is excellent, some flash memory cards include Error Correction Code (ECC) checking to detect single bit errors in data. High quality manufacturers will make sure their rated error specifications are less than 1 bit in 1,000,000,000,000,000 bits read. Low power consumption and faster performance than any other memory standard also lend to the dominance of flash memory types. Now to define the difference between each flash memory type available.

Flash memory types breakdown

CompactFlash (CF) Cards:

CF Type I device

CompactFlash (CF) were the first small form factor flash memory cards introduced in 1994. CF cards incorporate a controller, a small microprocessor to help control the device. Probably the most popular memory card on the market, CompactFlash cards are about the size of a matchbook and connect to products via 50 pinholes arrayed in two rows along one edge of the card. Type I cards are also compatible with CompactFlash Type II slots, and will fit in a standard PCMCIA (laptop PC) slot with the use of an inexpensive adapter.

CF Type II device

Type II CompactFlash is simply a thicker version of the Type I card and was designed to allow for higher memory capacity. Though some Type II cards (like almost all memory cards) have no moving parts, the most popular Type II card is the Microdrive, a miniaturized hard drive developed by IBM. Microdrives are available in capacities of up to 1 GB. Because Microdrives have moving parts, they are less rugged, more heat-sensitive, and require more power than their Type I counterparts. For these reasons, a product with a Type II slot is not necessarily Microdrive compatible; please check your owner’s manual or the product manufacturer’s Web site to be certain. The extra thickness means that Type II CompactFlash cards will not fit in a Type I slot. Type II cards are primarily used in high-resolution digital cameras from Canon, Nikon, and Casio. The CompactFlash Association sets the specification for CF cards.

CF Type II Device

Interface Max. Capacity Voltage Pin Count Size in MM
CompactFlash (includes built in controller) 1GB (Type II) 3.3 and 5 Volts 50 36.4×42.8×3.3

SmartMedia Cards (SM)

SmartMedia cards, introduced in 1996, are the thinnest for factor flash storage devices. They were originally called SSFDC for Solid State Floppy Disk card, as they look like a miniature floppy disk. SmartMedia cards usually incorporate a single flash chip and do not incorporate a controller, thus they depend on the host controller in the PDA or Digital Camera to manage all the memory reads and writes. Nearly always black in color, SmartMedia cards are as thin as a credit card, about the size of a matchbook, and can be easily identified by the gold-plated contacts that take up nearly half of one face.

Interface Capacity Voltage Pin Count Size in MM
SmartMedia (no built in controller) 128MB 3.3 and 5 Volts 22 45x37x0.76

SecureDigital (SD) Cards

SecureDigital was introduced in 2001 and is the newest form of compact flash memory storage available on the market today. SD is a second generation of the MultiMedia card standard that is backward-compatible with MultiMedia Cards MMC. The SD format includes several technological enhancements over MMC. Such advantages include the addition of cryptographic security protection for copyrighted data/music and a 4X increase in data transfer rates — SD is fast! The SD card association sets the specifications for SD cards. To help-support higher-capacity cards, SD cards are slightly thicker than the original MMC. This means that devices designed to support SD may also accept MMC, but devices exclusively designed for MMC will in general not support the thicker SD cards.

Interface Capacity Voltage Pin Count Size in MM
SecureDigital (includes built in controller) 512MB 2.7 and 3.3 Volts 9 32.4x24x2.1

MultiMedia Cards

MultiMedia Cards are the smallest flash cards available, they are about the size of a postage stamp. MMC was introduced in 1997 and initially used in the mobile phone and pager markets. Today they are commonly used in digital cameras and MP3 players, rarely so in PDAs. The MultiMedia Card Association sets the specifications for MMC.

Interface Capacity Voltage Pin Count Size in MM
MultiMedia Card(includes built in controller) 256MB 3.3, 5 and 12 Volts 68 32x24x1.4

Sony Memory Stick

Sony has always been the renegade that wants to set its own standards, and often they do help shape industry by doing so. In the world of flash memory, Sony has taken the same route of inventing their own type of card for digital storage and that card is called a Memory Stick. The Memory Stick is about the size of a stick of chewing gum

Interface Capacity Voltage Pin Count Size in MM
Memory Stick(includes built in controller) 256MB 2.7 – 3.6 Volts 10 50×21.5×2.8

Average Price for 128MB of each memory

Price is very important too, here is a breakdown on how much it would cost to get 128MB of storage for each memory type.

CompactFlash: $54

SmartMedia: $50

SecureDigital: $75

MultiMedia: $75

Memory Stick: $75


So which type of memory is best? SecureDigital is certainly the newest and the best without question in terms of performance, it’s faster and more secure than any other type of flash memory. CompactFlash offers the opportunity for mass storage with the microdrive options and is cheaper than SD in terms of price, so that is very attractive too. Memory Stick is good and should not dissuade you from buying a Clie, especially if you have other Sony products. Remember, you can transfer all your files from these Storage types by way of your PDA or a card reader that interfaces with your computer and is available for each memory type described above. Buying a PDA that offers dual memory expansions is definitely optimal, otherwise, looking for SD memory expansion is a wise move.



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