|Everything HP200LX: Knowledge, Products, Service|
HOW TO USE: RAM Memory Cards
How do you use them? What files should you store on them? What do you need to watch out for? What's the difference between SRAM and Flash ROM cards?Inserting a RAM Card in the HP 95LX: Graphic
Last issue (page 10) we took a look at expanding the storage of your HP 95LX with the addition of a RAM memory card. This issue, I would like to focus on its use, including specific strategies and concerns.
General Points on RAM Cards
There are some general points that pertain to a RAM card, regardless of the kind you are using.
Static Random Access Memory cards (SRAM) are by far the most popular cards available for the 95LX. Their only limitation is that their data is preserved through the use of a lithium backup battery that keeps the microchips in the card "alive." These batteries generally last for a year and are cheap enough, costing about $3.
There are a few things you should be aware of when using SRAM cards with the HP 95LX.
Change the Backup Battery Every Ten Months
Power is supplied to the card by the 95LX only when the 95LX is on. If the card is removed or your 95LX is off, the card's memory is preserved by its internal battery. Even though a card battery may last a year, change the battery more often!
The 95LX was designed before the current series of RAM cards. The Palmtop cannot respond to the intermediate low battery signal that the newer SRAM cards deliver when getting low on battery power. Instead it can only respond to the final low battery signal sent by the card. This is a point at which your SRAM card may lose its data. It is my recommendation that the SRAM cards backup battery be changed ten months after it was installed, regardless of its condition. Set an APPT alarm reminder.
What to Do If You Get a Low Card Battery Warning
The first thing to do is to try and keep the HP 95LX on. Immediately connect it to the AC Adaptor or turn off its timeout function using programs such as TIMEOUT , SWITCH!, or 95BUDDY . Many SRAM cards will then let you replace the card's backup battery while it is still in your 95LX. A little slide lock or screw holds the retaining ring for the battery. By releasing the ring the battery can be removed. PLEASE note whether the old battery's plus side is up or down and insert the new battery the same way. Also, remember to re-lock the retaining ring to prevent removing it while trying to unplug the card.
Maximize a SRAM Card's File Storage Capability
When SRAM cards are formatted, they are divided up into storage units called "sectors" and "clusters." Each sector on a SRAM card has 512 bytes. Each cluster has one sector.
Any file takes up a minimum of one cluster, or 512 bytes. A small batch file of a few lines may require less than 50 bytes of storage space. However, it must occupy at least on cluster, or 512 bytes on your SRAM card. A 520-byte text file can't quite fit into one cluster, so it must occupy two clusters, or 1,024 bytes.
This fact means that it is very wasteful to store many small files on your RAM card. If you use MEMO to keep scraps of information and save each to a separate file, you're wasting precious space. You should check out programs like fastNOTES (ad page 39 this issue), Keep-In-View (ad page 48, Nov/Dec 92 issue) and NOTES95 to recover that expensive real estate.
Unfortunately, the DIR command of DOS reports the space required for storage, not the space actually used (i.e. it reports the small batch file as taking up 50 bytes, not the 512 bytes it's really occupying). DIR also reports the "bytes free," the remaining storage space. It subtracts the space needed for each file (not the space actually occupied) from the total bytes available. If you have many small files stored on your card, this "bytes free" figure can be way off.
On last thing: You may have no more than 63 entries in the root directory, A:\, of your card. If you want to store more files on a card, you have to put them in a directory.
A variation of the SRAM card is the DoubleCard marketed by ACE Technologies (see add, back cover this issue). This card has onboard compression software from STAC Electronics. While it offers "plug-n-play" installation, there are some things about this card you should be aware of. First, there is a startup file on the card called CONFIG.SYS. This can be seen by inserting DoubleCard in the card slot, and pressing (FILER) (F5) b:\ (ENTER) (ENTER). The B: drive displays the uncompressed portion of the card, the A drive shows you the compressed portion. If you want to have an AUTOEXEC.BAT file processed when booting with this card, the AUTOEXEC file has to reside on the compressed portion of the drive (A:\). In addition, the following line must be added to CONFIG.SYS on the B drive (NOTE: make sure there is an space between "COMMAND .COM" and "/P".)
Device drivers referred to in CONFIG.SYS prior to the Stacker command line must reside on the uncompressed portion (B:) of the card if the A drive designation is used. Any files loaded after the Stacker command line must reside in the compressed portion (A:). All programs that are called from the AUTOEXEC.BAT file should reside on the compressed portion of the card, or the 95LX's C drive.
If you store confidential information on your 95LX, it's important to be able to secure your data. ACE provided Password protection with their DoubleCards. (Stacker 3.0's password protection cannot be used on the 95LX.)
The DoubleCard can compress your C drive, if you wish. I am opposed to doing this for several reasons. First, once you have created this compressed "G" drive you may not change your System RAM/Drive partition without destroying the drive. Next, you cannot put an APNAME.LST on this drive. Also, since the G drive is really one big file, if it gets corrupted you will probably lose all of the files instead of individual ones. Finally, you can achieve most of the space-saving benefits by first compressing .COM and .EXE files with DIET or PKLITE , and then storing them on the C drive. If they corrupt, or you lose them you can easily replace them. Besides, they don't compress very well with Stacker. Storing compressed .EXE and .COM files on your C drive leaves more room on your card for your highly compressible data files.
The final feature incorporated into DoubleCard is built-in reset protection for your C drive. Every time a hard reboot is performed (by pressing (CTRL)-(<Shift>)-(ON)) four bytes in your C drive get corrupted, if you are using a 512K 95LX or a 1MB Palmtop with system RAM set to less than 512K. As long as the DoubleCard software is in memory those four bytes will not get corrupted.
Sundisk Flash ROM Cards
At the time this article was written, the only Flash Technology entry that may be used on the 95LX is from Sundisk (see ad, page 10 this issue). This card has the advantage of not needing a battery to retain its data, however it does require its software driver be in memory in order to read it. The result of this is that you must have its driver either on C: drive or on a SRAM card when you reboot your 95LX. Sundisk is planning to include a ROM card to be used when rebooting, after which you can insert the Flash card.
The Sundisk card is available with or without Stacker compression software. As delivered, the card is formatted with large, 4K clusters. This has no impact on disk space if you are using Stacker, but it has a big impact if you are not. (See the discussion of cluster size above.) Sundisk may make available a utility that can format the Sundisk card with the smaller, 512 byte clusters.
If you decide to use Stacker on the Sundisk card, I recommend altering the way that Sundisk sets things up. As installed by its installation program, the STACKER.COM file is stored on your C drive. This is not preferred because the file is large, and the corruption of the C drive would make it difficult to access the compressed files on the card. A better strategy is to have STACKER.COM reside on the card. This can be done by following these steps:
Another issue concerns the use of the Sundisk cards regards the AA batteries used in your 95LX. The Sundisk card requires a higher current than SRAM cards to write to it. The device driver, SDPDRV.SYS, does include a battery check routine to make sure there is enough left in the batteries before the write is started. Versions 1.1 and 1.2 of SDPDRV.SYS put the card into a write-protect mode when the battery was low, causing the card to be corrupted under certain circumstances. Version 1.3 and above turn the 95LX off. Unfortunately, 1.3 and above are only setup for alkaline battery use. The best solution that works on all versions and battery types is to use BATTman from ACE Technologies. It will safely turn off your 95LX under all conditions that I have tested.
Finally, it is very possible that the current HP 95LX Sundisk cards will not work with future palmtops.
Memory Card Drives
Card drives are floppy-drive-like devices that attach to your PC and let your read a RAM card like it was a floppy disk. They come in internal (mounted in a floppy drive slot) and external (connect to the desktop via a cable).
The Databook Thincard Drive is an example of an internal floppy drive. It offers great flexibility in the range of cards that it supports. It's attached to the PC bus, so it's very fast. The only problem I found with it was that if a card was in the drive when I turned on my PC, it sometimes corrupted the card. Otherwise, it was a dream to use and makes backing up your card a simple procedure.
Both Databook and Adtron offer external card drives that connect to the PC's parallel port. I did not receive the Adtron in time for this review, but the DataBook drive is very well implemented. It comes with two DB25 parallel connectors and an AC adapter. This allows you to use one port for both your card drive and printer. While its performance is definitely slower than that of the internal drive, it's a lot faster than using anybody's' file transfer software (for more on file transfer software, see page 12 this issue). Also, if you are at all squeamish about opening up your PC, the external drive is a snap to install.
Both types of drives require a device driver installed in the PC's CONFIG.SYS file in order to read cards. Make sure the one you select will support the type of cards you want to use. Currently, Databook's software will support both SRAM and the Sundisk cards.
RAM Cards More Attractive As Prices Fall
With prices falling monthly this form of storage will gain in popularity. This will cause further price drops. The RAM card in any of its flavors is the best place to keep your data files. It is impervious to vibration and shock, and offers significant speed advantages over mechanical drives. The ability to have 20MB of storage in the equivalent of a credit card offers tremendous productivity potential. The different card technologies require different strategies to optimize their use and enhance their reliability.
Copyright © 2010 Thaddeus Computing Inc