Specifications
22
USB flash drive available. It is 40% smaller than a miniSD in area and about 18% smaller in
volume. Despite the small size, the miCard has a total capacity ranging from 128MB to 8GB
with a “theoretical” capacity of 2048GB. That’s 2 terabytes of storage! The miCard uses a 16-
bit bus rather than the 4-bit or 8-bit buses used in SD and MMC cards, and that 16-bit bus
allows sequential speeds of up to 60MB per second with a “theoretical” speed of 120MBs once
the internal interface of NAND chips can be sped up. Although the miCard is a USB 2.0
device, its power consumption is significantly lower than that allowed by the USB 2.0 standard.
In those cases where a USB 2.0 port is not available, an adapter converts the miCard USB
drive to an SD/MMC card.
The open standard has kept MMC alive, but it has also led to a proliferation of flash cards that
can confuse consumers.
SECURE DIGITAL CARDS
The Secure Digital card is almost identical to the MultiMedia card, but it has several features the
MMC card does not share. The most significant was supposed to be its compliance with the
Secure Digital Music Initiative specification (SDMI) to protect specific copyrighted material, but that
format is no longer being promoted since the copy protection code was cracked. SD audio devices
may still require audio encryption, and that eliminates MMC cards as in such devices. Some SD
cards that contain encrypted audio files will not allow other types of files, such as picture files, on
the same card. A second feature is a mechanical write/protect switch on the card to prevent
accidental erasures, similar to the write/protect tabs found on floppy disks. SD cards have faster
read and write speeds than MultiMedia cards, and this advantage in addition to its features has
Figure 10
Number of 4-Minute Songs on Flash Devices
MP3
Compression
(kbps)
audio quality 8MB 16MB 32MB 64MB 128MB 256MB 512MB 1GB 2GB
360 excellent 0 1 3 6 12 24 48 97 194
256 excellent 1 2 4 8 17 34 68 136 273
224 very good 1 2 4 9 19 39 78 156 312
192 very good 1 2 5 11 22 45 91 182 364
160 good 1 3 6 13 27 54 109 218 436
128 standard 2 4 8 17 34 68 136 273 546
112 fair 2 4 9 19 39 78 156 312 624
96 fair 2 5 11 22 45 91 182 364 728
80 poor 3 6 13 27 54 109 218 436 873
64 poor 4 8 17 34 68 136 273 546 1,092
56 very poor 4 9 19 39 78 156 312 624 1,248
48 very poor 5 11 22 45 91 182 364 728 1,456
32 forget it 8 17 34 68 136 273 546 1,092 2,184