Sandisk Standard SD Card 2GB
Contents
1. Symptoms Why is the capacity of my Secure Digital memory card as reported by many operating systems different than the capacity that is listed on its label Affects Description Sandisk products Secure Digital Operating systems All Microsoft Hardware platform All PCs Jornadas etc Cause The operating system when reading the size of the card reports a slightly different capacity than what is listed on the card s label SD has a small overhead for the security features Solution Definitions of a Megabyte 1 Operating Systems commonly define a Megabyte MB as 2 to the 20th power 1 024KB Kilobytes 2 DiskDrive and Flash Memory Card Manufacturers commonly define a MB as one million bytes exactly 1 000 000 bytes Unformatted Capacity Also known as drive byte capacity before formatting The Maximum capacity of disk drive before formatting equals Cylinders X Heads X Sectors X Bytes per Track Example 64MB CompactFlash Card consists of 490 Cylinders 8 Heads 32 Sectors 512 Bytes per Track This equates to 490 X 8 X 32 X 512 64 225 280 Unformatted Capacity 64 225 280 bytes Formatted Capacity 63 934 464 bytes User Data Cause Disk Drive Companies such as SanDisk define 1 MEGABYTE as 1 000 000 BYTES Operating Systems define 1 MEGABYTE as 1 048 576 BYTES 1024K X 1024K or 2 to the 20th power Example SanDisk 64MB CompactFlash Card being r2. ead by Microsoft Operating System SanDisk Total Formatted Capacity divided by 1 MB as defined by the Operating System equates to the following 63 934 464 BYTES 1 048 576 BYTES 60 972 656 BYTES 60 9MB displayed by OS Security overhead SD 8 The total card capacity of 8 million bytes is divided into a security area and a user accessible area of approximately 6 7 million bytes SD 16 The total card capacity of 16 million bytes is divided into a security area and a user accessible area of approximately 14 6 million bytes SD 32 The total card capacity of 32 1 million bytes is divided into a security area and a user accessible area of approximately 30 5 million bytes SD 64 The total card capacity of 64 2 million bytes is divided into a security area and a user accessible area of approximately 62 3 million bytes SD 128 The total card capacity of 128 4 million bytes is divided into a security area and a user accessible area of approximately 125 8 million bytes
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