Flash memory
Flashcards are solid-state storage devices, mostly used in small mobile devices such as MP3 players, digital photo and video camera's and in other portable devices such as PDA's. Through external card readers, PCMCIA-adapters or proprietary slots, the flashcard data can be read in notebooks/PCs.
Their typical size is a large postage stamp. Storage capacity is typically 64 or 128 MB, but 1 Gb also exists and 2Gb is at the horizon . Basic types are Compactflash, Smart Media, Multimedia, Secure Digital and Memory Stick. The memory device (NAND-Flash) mainly comes from Toshiba, Samsung or Hitachi. The only competing technology for this type of application is the miniaturized hard disk drive, such as e.g. IBM's Micro Drive.
Because flashcards are used in battery operated devices, energy consumption is a big issue. Recent (2002) consumer tests compared 20 flashcards, as well as the MicroDrive, on read/write data transfer rates as well as read/write energy consumption.
Data transfer rate
Read data transfer rate ranged from 1 to 3.7 Mb/s (compare MicroDrive 3.6 Mb/s), with an average of 2 Mb/s for a typical 128 kB card. Best was the largest card: a 512 kB Pixomedia. Write data transfer rates usually are around 30-40%25 lower, but with the best (2.6 Mb/s, Sandisk) writing was hardly slower than reading.
Power
Power consumption during reading ranged from 0.05 to 0.4 W (average 0.15 W). Worst was the fastest reading 512 kB card, which consumed 0.4 W. IBM's 1 Gb MicroDrive consumed 1 W. During writing, power consumption was similar.
Standby energy consumption varied between 0 and 0.2 W (!), with an average of 0.05 W. (MicroDrive 0.08 W)
Energy
To compare flashcards on energy consumption you need both the power consumption and the data transfer speed. Reading energy consumption was between 0.15 and 0.4 Wh per Gb of data transferred. Writing energy consumption was between 0.3 and 1.5 Wh per Gb of data transferred. As a comparison: The MicroDrive used 1 Wh reading 1 Gb of data and 2 Wh writing 1 Gb.
Future
In The coming years flashcard storage capacity will probably grow to match present hard disk drive capacity in notebooks (15-20 Gb) and may actually become a real substitute because of its low energy consumption. Alternatively they will become the preferred storage medium for enhanced PDAs. Only the future will tell whether functionality of those PDA's will then be enough to convince mobile consumers not to buy a notebook any more and/or leave the notebook at home to replace the desktop.
Courtesy of the French Energy Agency ADEME, Future Electronics project.
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