#12 Article: Expansion Cards

Expansion cards are more popular than ever.  Pocket computers, digital cameras, some MP3 players, and other popular devices use Compact Flash, Secure Digital, Memory Stick, SmartMedia, and other card formats.  Digital cameras are commonplace, with 12.5 million sold in the US in 2003, compared with 12.1 million film cameras.  Expansion cards may contain a miniature camera or Wi-Fi transceiver, but most are memory cards.  Some new cell phones use a new, tiny memory card, about the size of the nail on your little finger.  And more expansion card formats are on the way.


I used to prefer smaller capacity memory cards.  “Smaller” is relative.  Sandisk recently announced an 8Gb Compact Flash card; any cards under 1Gb are now considered “small.”  My reasons for preferring smaller cards: 1) If I had all my data on one card, and it failed or was lost, I lost all data that wasn’t backed up at home.  2) Two 64MB cards were cheaper than one 128MB card.  3) I assumed the time to find data, read the data, then write back to a small card should be the same or marginally faster than a larger card.  And that last reason was partially wrong!


What seems logical isn’t.  The complete backup of one of my pocket computers to a 256 MB Secure Digital card is quite fast, but backups to a 128 MB card seem to take forever.  I thought the 128 MB card must be defective.  Then I came across a discussion on an Internet message board where others noted the same phenomenon.  The consensus is that the circuitry in 256MB or larger cards is different, and faster.


Backing up a total of 276 files on a PalmOne Tungsten T3, backup size = 11,366 KB, here are my results: 1} Sandisk 256 MB Secure Digital card = 60 seconds.  2} Toshiba (labeled Kingston) 128 MB Secure Digital card = 326 seconds.  Both cards are defragged and contain other content in addition to the backup sets.


There are several values to measure for speed, and variables such as the card manufacturer and the device using the card.  One popular utility measures the following speeds: file create, file write, file read, file seek, DB export, DB import, record access, resource access, file delete, and an average “total.”  A particular card may be fast at some tasks, and lag far behind similar cards in other measurements.  Another confusing element — you loved the last card you purchased with the ***** brand name, and can’t figure out why this new card of the same brand and capacity is a dog.  There are only a few actual producers of these cards (Sandisk, Panasonic, and Toshiba), and they label them for many other companies: Dane-Elec, Delkin, Edge, Kingston, Kodak, Lexar, Memorex, PNY, PQI, SimpleTech, SmartModular, Viking, and other brands.  Some reselling companies buy their cards from more than one manufacturer, so cards with the same brand name may not be the same.  Also, manufacturers sometimes change the processes and internal components used to make the cards.  If you buy a card that seems slow or flaky, and other cards work fine in the same device, promptly return the new card for another brand.  The posts on several Internet forums preferred Panasonic and berated SanDisk, both actual card manufacturers.


Sandisk does rate highly in at least one category: low current draw, at least with their Compact Flash cards.  Just as speed varies between cards, the current draw to read and write data to the cards varies.  Some cards also draw current whenever they are in a device, draining the device’s battery.


You may think it strange that card speeds and current draw can vary widely.  Even stranger, not all cards work in all devices.  This has markedly improved with newer devices and expansion cards – two or three years ago Internet message boards were filled with users commenting on which brands and capacities of expansion cards worked and which didn’t in particular devices.  Even more confusing, a brand/size that worked in one device may not work in another very similar model from the same manufacturer!


If this isn’t confusing enough, some formats now have two types of flash memory cards: Regular and High Test – speed that is.  The “Professional” version is much faster than the regular version.  You don’t need this speed for use with a handheld computer, but it may be worth the extra cost for use with a digital camera.


The first memory card I purchased for a handheld was 32Mb.  The most recent card I purchased was 512 Mb.  That’s another reason for buying larger cards — to fulfill a universal law — your collection of programs, photos, e-books, and other data will expand to fill the card, no matter what the capacity!




About pdacomputing

Small business owner in Pittsburgh, PA. I've used different mobile platforms over the years; currently using 2 very different platforms.
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