Specifications

Smart Media chips use just one NAND memory chip in the card. If an SM card needs greater

capacity, it simply uses a NAND chip that offers that capacity rather than stack chips as other flash

cards do. Smart Media cards also differ from other flash cards in their ability to withstand shocks.

Their shock limit is half that of the larger card—1,000 G.s of force versus the Compact Flash limit

of 2,000 G.s. The advantages of Smart Media lie in their smaller design, lighter weight (one-tenth

that of the Compact Flash card) and simpler construction.

There are two versions of the Smart Media card that differ in the voltage of the power supply they

require. A notched corner on the lower left side means the card works with a 3.3-volts power

supply. A notch on the lower right side indicates a 5.0-volt card. Some devices will work with

either 3.3V or 5.0V cards, but consumers should check to make sure that they select the proper

SM card. The 5.0 versions usually do not fit into devices requiring the 3.3V card.

MULTIMEDIA CARDS

If smaller size is a virtue, the MultiMedia card holds a big advantage. By using Toshiba’s NAND-

based memory chips instead of Intel’s larger NOR-based chips used in Compact Flash, MMC

cards could be far smaller. This flash memory card is about the size of a postage stamp, the

smallest, thinnest, and lightest of the memory cards until the micro versions were introduced. For

that reason they are commonly used in portable MP3* players, mobile phones, and other hand-

held devices that are also small and lightweight.

*MP3 (Motion Picture Experts Group, Layer 3) is a compression scheme for audio signals that has different

levels of compression that increasingly eliminate audio signals that listeners are not expected to be able to

hear. The audio data transfer rate for uncompressed CD signals is 1,411.2 kilobits/second (16 bits/sample x

2 channels x 44,100 samples/second), but this rate creates very large files. In order to transfer audio on the

Internet or to store as smaller files, compression schemes reduce file sized by eliminating portions of the

signal that listeners are not likely to hear. One example of eliminated sound would be low-level, high

frequency signals masked by louder sounds at lower frequencies to which human ears are more sensitive.

This type of compression is known as “lossy” compression because once the signal is modified, the missing

parts cannot be restored. Reducing the 1,411.2 kbps rate of CDs to 320 kbps brings the files down to a

more manageable size with little to no audible change to the sound. It is not “CD-quality,” however, no matter

what the advertising hype claims, because data have been lost. MP3 files of 320kbps are still rather large;

and there are additional compression schemes of 256, 224, 192, 160, 128, 112, 96, 80, 64, 56, 48, and

32kbps further reducing the file size and the audio quality. The general standard for an acceptable balance

of MP3 sound quality and small file size is 128kps. The actual sound quality depends greatly on the decoder

used to play back the digital signal as well as the compression level. Figure 10 is a chart with a rough

approximation of the number of minutes of music one can expect to store on different capacities of flash

cards.