Product Description

Symptoms:

Why is the capacity of my flash memory card (as reported by many operating systems)

different than the capacity that is listed on its label?

 

Affects:                                              Description:

Sandisk products:                                     CompactFlash

                                                      SmartMedia

                                                      Multimedia

                                                      PC card

                                                      Ultra CompactFlash

                                                      Memory Stick

                                                      Memory Stick Pro

                                                      Memory Stick Duo

                                                      Extreme CompactFlash

                                                      Ultra II CompactFlash

Operating systems:                                    Most

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

 

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 read 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.