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It's been two years, and you have evolved. Your PDA now has to be a music player, video player, and PIM client. You have emails to manage, PowerPoint presentations to edit before the meeting, and a few maps to that meeting to save. Simply put, two years ago PDA buyers had to consider memory. And with many PDAs then offering memory expansion in different forms, it was more confusing to decide which PDA to buy.

Since then, the flash memory wars have cooled off some (now the major formats are Secure Digital (SD) and Compact Flash (CF)). But, the choices are harder than ever with ever lowering prices and sub-formats of some of the major ones. So leave it to BargainPDA to get you up to speed on the different memory types, and which PDAs support what type. If you are into carrying a lot of data, this guide should help you in making a memorable choice.

What is Flash Memory?
Flash memory is a type of data Storage technology that uses no mechanical parts (like a hard drive or floppy disk), but uses electrical currents stored in blocks to save data. The fact that it is not mechanical also lends to flash memory's most attractive components: it is extremely durable, there is zero noise produced from writing or reading data, and flash memory cards use very little power. Flash memory also performs faster than other memory types. These properties of flash memory have made it a great alternative to solid state memory types for data storage.

Another aspect of flash memory is that it's very compact; meaning that it can be placed into smaller casings and therefore work for more devices. Below, we will look at the different types of flash memory by their frequency of use today. This list will look very different from two years ago when we last looked at flash memory. But it will also show some of the trends that memory companies and device manufacturers are taking with their products.

Compact Flash (CF) Memory

Compact Flash (CF) memory was the first type of flash memory format available. Because of the explosion of digital cameras that use CF memory, it has become the most popular type of memory format used. With PDAs, CF memory only took off with Windows Mobile/PocketPC devices (there was only one PalmOS company that made CF compatible devices, HandEra, but they no longer produce PDAs). Though many WinMobile devices have moved to using Secure Digital memory, there are still models, such as the Asus LOOX 720 and Dell Axim X50 series models, which use CF memory.

There are two types of CF memory (up to 4GB in capacity). The first is CF Type I cards. These were the first type, introduced in 1994. They are most popular because they look just like little matchbooks. Type I cards will fit into Type I and Type II memory slots. The second is Type II. Type II was introduced to allow for higher memory capacity. Many PDAs today accept Type II cards as those slots will also accept Type I cards. One other benefit of the Type II card size is the Microdrive. The Microdrive is not a flash memory card, but a hard drive that is the size of a Type II CF card. It comes in a 4GB version, though higher capacities are in development.

Secure Digital (SD) Memory



Secure Digital (SD) memory is the newest form of flash memory and has taken off as the standard kind of expansion memory used in mobile devices. At about the size of a postage stamp, SD cards are the second generation of the MultiMedia Card (MMC) standard. Being the second generation, it includes some newer features such as, cryptographic security protection for copyrighted data/music and a 4X increase in data transfer rates. These additions, along with growing capacities (2GB) and lower costs (1GB cards are less than $100) have made SD cards the fastest growing segment of flash memory.

Usually when buyers see a PDA that takes SD cards, they will notice it supports SDIO. SDIO means Secure Digital Input/Output. The specification allows SD card slots to also take other hardware devices besides memory cards. The most popular accessories that use SDIO are Bluetooth and WiFi Wireless Network cards, FM radio receivers, and cameras.

There is another version of SD cards that are called High Speed. Basically, these cards have faster read and write speeds which are needed for cameras and other multimedia devices that need to transfer large files. High Speed cards cost more than the non High Speed ones, but unless you are swapping your SD card between your camera and PDA, you will not need the extra speed. The SD card also has a smaller version called mini-SD that is about half the size of a regular SD card. You will find them on some mobile phones, but to date there are no PDA companies that use mini-SD cards.

Memory Stick (MS) Memory



Of the different flash memory types, there is probably none more confusing that the Memory Stick (MS) Card. Sony developed MS flash memory cards as chewing stick-sized competitors to the SD card and for a while it was a good competition between the two. But due to the Sony really being the only company pushing MS memory in the US, the cards have largely been seen only in Sony products. That would be a good thing for Sony if there weren't so many different types of MS cards.

Original Memory Stick
The original cards were only designed to handle up to 128MB of memory. Most Sony products that accept removable media support this version of MS, though if you want to hold video or large amounts of data, you will need a different form of MS

Memory Stick Select
Sized the same as the original MS, the MS Select has two 128MB chips on one card. Each is treated as a separate card by the reading device. But again, this only gives a total of 256MB of space which is good for pictures and music, but if are recording or viewing video, you will need more space.

Memory Stick Pro
MS Pro is the latest generation of the full sized MS memory cards. Supporting capacities of up to 1GB and having higher read and write speeds than the original MS and MS Select, it makes for an excellent alternative for those with Sony hardware who need more space. It is priced about $10 more than similar capacity SD cards.

Memory Stick Duo
MS Duo is Sony's answer to mini-SD. Its use is mainly found in mobile phones, and primarily in Japanese markets. Like the original MS, it can only support up to 128MB per card, but Sony does have an adapter so that devices without an MS Duo slot can use MS Duo cards.

Memory Stick Pro Duo
In the same way that MS Pro is an upgrade to the original MS, MS Pro Duo is an upgrade to the first generation MS Duo cards. Currently, the supported capacity is 2GB, as with SD cards. The prices for these cards are higher than comparable SD cards.

Magic Gate Memory Sticks
Magic Gate MS cards were designed to address the issues of digital rights management (DRM), a type of security for digital files supported by the music and movie industry. Magic Gate cards allow one to be able to play encrypted ATRAC and MP3 files on the device that has the MS slot. It used to be separate cards that were Magic Gate compatible, now, all of Sony's MS Pro and MS Duo cards support Magic Gate.

High Speed MS Pro/MS Pro Duo
Like SD cards, Sony offers High Speed cards that offer faster read and write speeds. They cost more than the non-High Speed versions, but most who are not swapping the cards between cameras and PDAs will not have a great need for them.

Other Non-volatile Memory
With the introduction of the PalmOne Tungsten T5 and Treo 650, there is the adoption of flash memory as the main memory within PDAs. Though there have been some PocketPC devices that have used non-volatile (NAND) memory in part. The T5 and Treo650 are the first to use NAND memory as the main working memory. Instead of stating again what has been typed, I will refer you to this type of memory written by Red Mercury (the creators of famous games such as Atom Smash and Acid Solitaire) - here is the link to that write up: http://www.red-mercury.com/nvfs.html

Conclusion
So what memory card should you choose? Unlike two years ago when there was a easier decision to get a device that supports CF cards because CF cards were cheaper than the rest, nowadays, SD cards have nearly evened out the field. Add to that, more PDAs support SD memory than those that support CF memory. Of all of those that even offer CF memory, they all also have an SD slot so that you can use the SD slot for memory, and the CF slot for another peripheral. Right now, you can get a 256MB SD card for as low as $15, and the PalmOne Zire 31 ($150) supports SD memory. With availability like this, it is easy to make the decision to use SD cards. But if you need more than just memory, getting a dual slot device is the best way to go. Also be sure to take into consideration other devices you own, like digital cameras, so you can benefit from memory card overlap.

To get the latest prices for memory cards, visit our Memory Cards section. Input the price and type of memory card that you are looking for and a query will display the best prices and where you can find the cards.