Hardware

PDA memory storage basics

PDAs can be great productivity tools. But when their batteries run down, you lose whatever data hasn't yet been synced to the desktop. To remedy this problem, PDA makers now include slots for nonvolatile flash memory in their products.

One of the advantages of Palm PDAs is that they are RAM-based "always-on" devices. This is also one of their disadvantages. Because volatile RAM requires a constant current, when the batteries run down, your information is erased. You lose whatever data hasn't yet been synced to the desktop.

To remedy this problem, PDA makers now include slots for nonvolatile flash memory in their products. These memory cards retain data when the power is turned off. Your data can be backed up to the card and then restored in case of a power failure, or even a catastrophic operating system failure (such as dropping your PDA at the airport).

Not surprisingly, there is more than one type of memory used in Palm-based PDAs. Before deciding on a PDA purchase, review the extended storage options presented here.

Storage standards
Palm device manufacturers use four types of storage for their products. Listed in order from smallest to largest by type and PDA manufacturer, they are:

Making use of the CF interface is a hard drive made by IBM. Called a Microdrive, it fits HandEra PDAs and offers high-capacity storage.

Price and storage capacity
Figure A lists the suggested retail prices and common storage capacities of these nonvolatile memory cards. As the table shows, with the exception of Handspring's Springboard module, prices are competitive between types.

Figure A
Type Capacity Avg. Price at PriceScan.com
(multiple vendors)
 
Memory Stick 16 MB $20  
  32 MB $32  
  64 MB $45  
  128 MB $85  
MMC 16 MB $20  
  32 MB $35  
  64 MB $55  
  128 MB $85  
CompactFlash 16 MB $15  
  32 MB $30  
  64 MB $45  
  128 MB $65  
  192 MB $100  
  256 MB $120  
  512 MB $370  
IBM Microdrive 340 MB $200  
  512 MB $250  
  1 GB $370  
Springboard* 8 MB $60  
  16 MB $75  
* Prices from HandEra.com    

Based on the information in Figure A, here are a few tips to consider when purchasing a Palm-based PDA and nonvolatile memory.

PDA memory tips:
  • Before buying a handheld on the basis of storage price, check your PDA maker's Web site to see if a vendor's card is compatible with your PDA.
  • Springboard modules are the most expensive per MB and have the fewest capacity options. These factors increase the Total Cost of Ownership (TCO) for Handspring PDAs.
  • Given that most Palm OS handhelds only come with 8 MB of RAM, it would be reasonable for an enterprise to purchase 16 MB of external memory. This would allow data as well as backup sets to be stored. However, if users require storage for large databases or other media such as digital film, PC data, or video or music files, companies should budget for larger sizes.
  • CF cards have both the lowest cost per MB (up to 256 MB) and the widest range of storage capacities (more than are listed); however, only HandEra currently makes PDAs with built-in CF slots. HandEra PDAs include both CF and MMC slots for the most versatility.
  • For the highest capacity storage, IBM Microdrives are the cheapest per MB. With a PC card adapter, Microdrives also allow portable PC storage.
  • Only Sony CLIÈs use Memory Sticks. Investing in Memory Stick means making a commitment to Sony PDAs.
  • Adapters can accommodate many options, though they, too, add to the TCO (see Adapters, below).


Memory card specifications
These memory cards (IBM Microdrives) have the advantages of small size, portability, ruggedness, and good data rates for PDA use. Memory Sticks are the slowest (at present) and CF cards the fastest, but the differences between them aren't that critical. The following tables give basic specifications for comparison for flash memory types.

The Write and Read times shown are averages from a number of manufacturers' specifications. There are two types of data transfer rates: burst and sustained mode. Burst is a high-speed rate the machine can use under special conditions. Sustained speeds are the average data rate for the device. Not all specs showed both figures. Sustained rates will be less than burst speeds.

Table 1: Memory Stick Specs
Type Dimensions (mm) (LxWxD) Capacities (MB) Write/Read Speed (MB/Sec)
Memory Stick 50 x 21.45 x 2.8 8, 16, 32, 64, 128 1.8/2.45 (burst)

Table 2: MMC Specs
Type Dimensions (mm) (LxWxD) Capacities (MB) Write/Read Speed (MB/Sec)
MultiMedia Card (MMC) 32 x 24 x 1.4 8, 16, 32, 64 2.0 (burst)

Table 3: CompactFlash Specs
Type Dimensions (mm) (LxWxD) Capacities (MB) Write/Read Speed (MB/Sec)
CompactFlash (CF) 36.4 x 42.8 x 3.3 4, 8, 16, 32, 48, 64, 128, 192, 256, 384, 512 16 (burst)
3.5 (Max sustained)
Microdrive 36.4 x 42.8 x 5.0 340, 512, 1,000 2.6-4.2/2.6-4.2 (sustained)

Table 4: Springboard Specs
Type Dimensions (mm) (LxWxD) Capacities (MB) Write/Read Speed (MB/Sec)
Springboard Not available 8, 16 Not available

Adapters
By now, PDA and memory card makers have realized that users need portability. For those times you need cross-platform compatibility, such as when your enterprise has two types of handhelds with different memory cards, you can purchase adapters.

Some of the available adapters are:
  • CF to Memory Stick
  • CF to MMC
  • Springboard to CF, MMC, or Memory Stick

These adapters let you use a PC as a middleman:
  • PC card to CF, MMC, or Memory Stick
  • Firewire, USB readers for CF, MMC, or Memory Stick

CF cards give the best value, based on price, speed, and capacity. Unfortunately, only one Palm-based PDA maker has gone the CF route—HandEra. Not as well known as its competitors, HandEra deserves a closer look. By having both an MMC and CF slot, the HandEra enables you to increase memory and add a peripheral at the same time. Many peripherals, such as bar code readers and wireless cards, exist for CF slots and are less bulky than their Palm or Handspring counterparts. However, if your storage and peripheral needs are modest, a PDA with either the Memory Stick, MMC, or CF formats will be sufficient.

Least attractive, in terms of memory, is the Handspring. The proprietary format, lower capacity, and higher cost of Springboard expansion modules make them less competitive.

Are PDAs a part of your organization?
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