Adding storage memory to your H/PC with a PC Card
Windows CE has been out for over a year and Microsoft has recently released version 2.0 of the operating system. Developers have begun to embrace Windows CE, providing more and more software solutions to enhance the usefulness of our PC companions. Unfortunately, the more software there is available, the more of it you want to put on your H/PC. This brings us up against the limitation of any handheld device -- internal memory.
The solution is simple: purchase a "storage PC Card" for your H/PC. Unfortunately, when you begin to ask vendors about such cards, you run into terms such as SRAM, FlashRAM, ATA Flash, and Series Flash, along with numerous card types described as Type I, Type II, Type III, CompactFlash, and Miniature. To compound the purchase problem, your H/PC manufacturer may not offer storage cards as part of their product line. In this article, I will try to explain these different terms and how they relate to expanding the storage on your H/PC.
Storage cards do not add system memory!
Before I start explaining what a storage PC Card is, I need to explain what it is not, and why I use the term "Storage PC Card." Many card vendors and even some manufacturers refer to this type of card as a "memory" card. I think calling it a memory card needlessly confuses users as to its purpose.
Any computer has two types of memory -- program Memory it uses to run programs and storage memory it uses to store programs and data when it is not using them. H/PCs come with 2 MB to 16 MB of internal RAM memory that can be partitioned between system memory (used to run the programs) and storage memory. (The System utility in your H/PC's Control Panel is used to partition this memory). There is one exception -- you can use a "Miniature Card" on a Philips Velo 1 to expand its internal memory.
A storage PC card adds additional storage memory and DOES NOT increase the amount of internal memory used by your H/PC to run programs -- well, not directly. What a storage PC Card gives you is another place to store files. (It's somewhat similar to adding another hard drive to your desktop PC.) You can move files and folders out of your internal memory and onto your card. This frees up internal memory, which you can then repartition as Program Memory.
All that being said, now for some specific advice on selecting a storage PC card for your H/PC.
1. Make sure it's the right size!
H/PCs come with different kinds of card slots. Most have a standard PC Card slot that accepts Type I or Type II cards (NOT Type III). The HP 320/360LX series and some of the newer Windows CE 2.0 machines come with Compact Flash slots. All the new Palm PCs have Compact Flash slots. Make sure you know what type your device has and get the appropriate card. Type I, II, and III PC Cards have the same width and height (roughly the dimensions of a credit card). However, they come in different thickness. (Type I, 3.3mm thick; Type II, 5mm; and Type III, 10mm). H/PCs accept Type I or II cards. Don't try to put a Type III card in your H/PC's card slot.
2. Select a card with a 3.3 volt or 5 volt operating current - not a 12 volt card!
Currently there are 3.3v, 5v, and 12v cards available. I do not know of an H/PC that can write to a 12v card (although they may be able to read from them). Many H/PCs, including those from Hewlett-Packard, are designed for 3.3v cards only. Higher operating voltages generally mean higher current draw, decreasing your H/PC's battery life. Lower is better and the 3.3v cards have the advantage.
You may also want to consider the read/write current of the storage PC Card. This refers to the amount of current the card draws when reading a file from a card or writing a file to a card. Cards today will draw from 30ma (milli-amps) to 90ma during a read or write. Again, lower is better, but this current does not significantly impact battery life.
Standby and Sleep current of the card also impacts your H/PC's battery life. Standby current is the amount of current that a card draws when it is not reading or writing data, but is "awake" and ready to do so. All cards automatically go into this mode when they are accessed by the computer. They stay in Standby mode drawing current for a predetermined amount of time and then automatically go into Sleep mode. Standby mode can last for quite a long period, drawing from 5ma to 35ma in the process.
Sleep mode requires the lowest amount of current from the H/PC, generally in the range of 2ma to 5ma. Any storage PC Card you purchase should have a Standby mode.
Unfortunately, you cannot predict a card's impact on your battery life by electrical specifications alone. Generally speaking, lower current requirements give you better battery life. But some cards, such as ATA cards, incorporate a "controller" that can reduce the read/write speed to increase battery life. Therefore, current consumption must always be viewed in the context of the number of bytes per second that can be read from or written to the card.
Generally speaking, manufacturers will provide information in the data or product sheets about the power management features of their cards. Their web site is an excellent place to search for this information when comparing brands.
Let's now take a look at the different storage technologies and how they stack up when used with an H/PC.
SRAM PC Cards work with any H/PC
Static Random Access Memory (SRAM) storage cards have the fastest performance of any storage PC Card and maintain very low operating currents. Because of this they are still very popular, although they are an older technology and a little more difficult to find. When an SRAM (pronounced "S" Ram) card is not being accessed, it does not draw any current. They are available in sizes from 128K to 4 MB, and work in any H/PC with a standard Type I or II card slot. They suffer two disadvantages not shared by other storage cards. In order for an SRAM card to maintain its data when it is out of your H/PC, or when your H/PC is turned off, it requires a lithium coin type battery to keep the card powered. These batteries should be changed once a year. Secondly, if you want to use the card in a Windows95 PC, additional drivers must be installed from your CONFIG.SYS file to support the card. Finally, while these cards are available in smaller sizes than other types, they are the most expensive on a $/MB basis.
Series Flash Cards
At the beginning of this article I went on for a bit about how storage PC Cards do not add system memory but that Miniature cards were the exception. Series Flash cards utilize flash chips in place of SRAM chips to eliminate the battery. While maintaining their data without power, flash chips do require their internal sectors to be erased before they can be written to. The management of this operation requires a separate driver and negatively impacts performance as the H/PC's microprocessor must manage the pre-erasing, and writing of the data along with program execution. As of this writing, the only cards available for the H/PC using this technology are the Miniature Cards used in the Velo from Philips.
ATA FlashRAM Cards
ATA FlashRAM cards represent the best combination of features and performance and are by far the most popular and prevalent storage cards used with H/PCs. Available in sizes ranging from 1 MB to 85 MB, these cards incorporate an ATA controller in much the same way as a mechanical IDE hard disk. As a result, there are no limits to size and the erasing of the Flash chips does not need to be handled by the H/PC microprocessor. On the down side, the built-in controller must be powered in a Sleep or Standby mode to access the card. The latest cards have reduced this current to a fraction of what it has been thereby reducing significantly the impact on battery life. These cards are also the most compatible with other PCs, making it easier to exchange data. Windows 95 and NT 4.0 come with built-in support for these cards. One word of caution: Older 12-volt ATA cards can still be found and these do not work with H/PCs. If you are looking at a used card make sure it is the newer 3.3v or 5v type.
Compact Flash Cards
Compact Flash storage cards are a relatively recent addition to the storage card scene. They are really nothing more than ATA FlashRAM cards in a compact enclosure. They have the characteristics of ATA cards (as described above) and your H/PC (or another PC) will view them as such. You can insert a Compact Flash card into a PC Card adapter and used them in the more standard Type II slot found in most H/PCs. Of the original H/PCs, only the HP 320LX has such a slot. Many of the new Windows CE 2.0 H/PCs and all of the Palm PCs and Auto PCs will include them. One important note: the original Windows CE 1.0 operating system only recognizes one PC storage card, therefore if your H/PC has a PC Card and CompactFlash slot only one can be used as storage. Windows CE 2.0 may correct this. (Note: the HP 360 and 620LX have both a PC Card and Compact Flash slot, and can access both at the same time.) Currently CompactFlash cards are only Type I but expect to see Type II cards in 1998 as they branch out to modems and pagers.
Using Your Storage Card
Whether you choose an SRAM or Flash card, once inserted, Windows CE displays an additional PC Card folder, representing the additional storage. (Windows CE does not use drive letters as in DOS and only one PC Card folder is available in version 1.0.). Upon inserting your card, you will get a pop-up message cautioning about using the card on batteries. This is normal, cannot be disabled and should not be of concern. Go ahead and answer "Yes". If your card was not formatted you will be asked if it can be formatted. Answering "Yes" will erase all data on the card. As distinct from the desktop version of Explorer you cannot reformat a card that has a valid format on it.
You move a file in Windows Explorer by selecting it, using the edit function to Copy it (Ctrl-C) or Cut it (Ctrl-X) when wanting to move, then go to the desired folder and Paste it (Ctrl-V) there. The PC Card folder is treated as any other folder on the internal drive. You can store data files, maps, docs and web pages there. If an application permits the selection of the installation location, you can install it in the PC Card folder. Once you have moved much of your data to the PC Card folder you can increase the memory you use to run programs (as described above). In my opinion, the most important function a storage card performs is as a quick way to backup your data. This is especially true of cards that use Flash chips and don't need a backup battery to keep to keep your data safe. If you're on the road and your PC companion's batteries die, a good backup of your data is a lifesaver! You can completely restore your files and configuration without a second PC, if you have it backed up on a card.
Care and Handling of Cards
PC storage cards are not like the hard drive in your PC. They are rugged and immune to vibration. They are however, electronic devices and should be treated as such. I know of no card that can survive a prolonged bath, being sat upon or stepped on and bent, or getting zapped by static electricity. The best place to keep your card is in your H/PC. Many cards come with plastic hinged boxes which should be used for storing them when they are not in a slot. It is helpful to remember that there are up to 68 tiny connections in the end of the card that must work if the card to function properly, and a PC Card is seldom repairable. Warranties can range from 1 year to lifetime, but every company has exclusions for physical damage.
I have not recommended specific brands or companies. Improvements come frequently and many companies simply put their label on a card manufactured by another company. The safe course is to always purchase a card that includes a return policy, just in case it proves unsuitable. With the information from a card's data sheet (usually available on the Web) and this article, I hope you will be able to make an informed purchase, maximizing your investment and getting years of use.
ABOUT THE AUTHOR
Mark Scardina is a Senior Product Manager for Oracle Corporation and Sysop of the HP Handhelds, HP PC, Palmtop, and Psion Forums on CompuServe. His Compuserve address is 76711,732. Or e-mail him at marks@ricochet.net