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Chapter 10. Flash and Removable Storage

Chapter 10. Flash and Removable Storage

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1 to a 0. Once a flash cell is programmed (that is, changed to a 0), the only way it can be changed

back to a 1 is by erasing it. The problem with this is that, although you can program individual cells

or pages, you can only erase cells or pages on a block basis, and a block usually consists of

thousands of cells (512KB in most cases). The actual programming and erasing process coaxes

electrons into and out of the transistor’s floating gate by a process known as Fowler-Nordheim


The two major types of flash memory technology are called NOR (Not OR) and NAND (Not AND).

Both use the same basic transistor (cell) design, but they differ in how the cells are interconnected.

NOR flash works more like dynamic RAM (DRAM), providing high-speed random-access

capabilities with the ability to read or write data in single byte quantities. NOR flash is the type of

memory used for flash ROMs, such as those found in motherboards, cell phones, and most devices

that have updatable firmware.

On the other hand, NAND flash works more like a storage device, reading and writing data in pages

or blocks instead of individual bytes. NAND flash is used in devices that store file-oriented data,

such as SSDs, USB key or thumb drives, digital cameras and digital film media, music players, and

more. NAND flash is denser than NOR flash, storing more data in a given amount of die space and

costing less overall for a given amount of storage.

The speed, low power requirements, and compact size of recent flash memory and SSD devices have

made flash memory a perfect counterpart for portable devices such as laptop computers and digital

cameras, which often refer to flash memory devices as so-called “digital film.” Unlike real film,

digital film can be erased and reshot. Ultra-compact, USB flash memory drives have all but replaced

traditional floppy drives, Zip/SuperDisk drives, and even optical discs for transporting data between


Several types of flash memory devices have been popular, including the following:

• CompactFlash (CF)

• SmartMedia (SM)

• MultiMediaCard (MMC)

• SecureDigital (SD)

• Memory Stick

• ATA Flash

• xD-Picture Card

• Solid-state drive (SSD)

• USB flash devices

Some of these are available in different sizes (Type I/Type II). Table 10.1 shows the various types of

solid-state storage used in digital cameras and other devices, listed in order of introduction.

Table 10.1. Different Flash Memory Devices and Physical Sizes

SSDs and USB flash drives are not listed because they do not have a single standardized form factor.

SSDs, normally used as hard disk drive (HDD) replacements, come in different form factors,

including the same form factor as 1.8-inch, 2.5-inch, and 3.5-inch HDDs as well as adapter card–

based versions that plug into a slot in the motherboard.


CompactFlash was developed by SanDisk Corporation in 1994 and uses the ATA (AT Attachment)

architecture to emulate a disk drive; a CompactFlash device attached to a computer has a disk drive

letter just like your other drives. When CompactFlash was first being standardized, even full-sized

hard disks were rarely larger than 4GB, so the limitations of the ATA standard were considered

acceptable. However, CF cards manufactured after the original Revision 1.0 specification are

available in capacities up to 128GiB. While the current revision 6.0 works in [P]ATA mode, future

revisions are expected to implement SATA mode.

The original size was Type I (3.3mm thick); a newer Type II size (5mm thick) accommodates highercapacity devices. Both CompactFlash cards are 1.433-inch wide by 1.685-inch long, and adapters

allow them to be inserted into laptop computer PC Card slots. The CompactFlash Association

(www.compactflash.org) oversees development of the standard.


Ironically, SmartMedia (originally known as SSFDC for solid state floppy disk card) is the simplest

of any flash memory device; SmartMedia cards contain only flash memory on a card without control

circuits. This simplicity means that compatibility with different generations of SmartMedia cards can

require manufacturer upgrades of SmartMedia-using devices. Now defunct, the Solid State Floppy

Disk Forum originally oversaw development of the SmartMedia standard.


If you use a SmartMedia-based Olympus digital camera that has the panorama feature, be sure

to use Olympus-brand SmartMedia because other brands lack support for the panorama feature.


The MultiMediaCard (MMC) was codeveloped by SanDisk and Infineon Technologies AG (formerly

Siemens AG) in November 1997 for use with smart phones, MP3 players, digital cameras, and

camcorders. The MMC uses a simple 7-pin serial interface to devices and contains low-voltage flash

memory. The MultiMediaCard Association (www.mmca.org) was founded in 1998 to promote the

MMC standard and aid development of new products. In November 2002, MMCA announced the

development of the Reduced Size MultiMediaCard (RS-MMC), which reduces the size of the

standard MMC by about 40% and can be adapted for use with standard MMC devices. The first flash

memory cards in this form factor were introduced in early 2004 to support compact smartphones. In

2008, the MMCA merged with JEDEC (www.jedec.org), which is the global leader in developing

open standards for the microelectronics industry.


A SecureDigital (SD) storage device is about the same size as an MMC (many devices can use both

types of flash memory), but it’s a more sophisticated product. SD, which was codeveloped by

Toshiba, Matsushita Electric (Panasonic), and SanDisk in 1999, gets its name from two special

features. The first is encrypted storage of data for additional security, meeting current and future

Secure Digital Music Initiative (SDMI) standards for portable devices. The second is a mechanical

write-protection switch. The SD slot can also be used for adding memory to Palm PDAs. The SDIO

standard was created in January 2002 to enable SD slots to be used for small digital cameras and

other types of expansion with various brands of PDAs and other devices. The SD Card Association

(www.sdcard.org) was established in 2000 to promote the SD standard and aid the development of

new products. Note that some laptop computers have built-in SD slots.

Reduced-size versions of SD include MiniSD (introduced in 2003) and MicroSD (introduced in

2005). MiniSD and MicroSD are popular choices for smartphones and can be adapted to a standard

SD slot. MicroSD is compatible with the TransFlash standard for mobile phones.

The original SD standard allowed for memory card capacities of up to 2GB. To support higher

capacities the SDHC (High Capacity) standard was created in 2006. SDHC supports cards from 4GB

to 32GB in capacity. To increase capacity beyond 32GB, the SDXC (eXtended Capacity) format was

released in 2009. SDXC supports capacities of up to 2TB. Note that devices are backward

compatible, meaning that a device that supports SDXC also supports SDHC and standard SD cards.

A device that supports SDHC also accepts standard SD cards, but such a device does not support

SDXC cards. Devices that support only standard SD do not support either SDHC or SDXC cards.

Sony Memory Stick

Sony, which is heavily involved in both laptop computers and a variety of digital cameras and

camcorder products, has its own proprietary version of flash memory known as the Sony Memory

Stick. This device features an erase-protection switch, which prevents accidental erasure of your

photographs. Sony has also licensed Memory Stick technology to other companies, such as Lexar

Media and SanDisk.

Lexar introduced the enhanced Memory Stick Pro in 2003. Memory Stick Pro includes MagicGate

encryption technology, which enables digital rights management, and Lexar’s proprietary high-speed

memory controller. Memory Stick Pro is sometimes referred to as MagicGate Memory Stick.

The Memory Stick Pro Duo is a reduced-size, reduced-weight version of the standard Memory Stick

Pro. It can be adapted to devices designed for the Memory Stick Pro.

Sony later released “Mark 2” certified versions of the Memory Stick Pro in 2008. This certification

indicated that the cards were suitable for use with AVCHD (Advanced Video Coding High

Definition) recording devices. Sony also released a smaller Memory Stick Micro (also called M2)

format in 2006, which was designed to compete with microSD. In 2009 Sony announced the Memory

Stick XC (eXtended Capacity) format in order to compete with SDXC.

Because the Memory Stick formats are proprietary and only used in Sony devices, I recommend

avoiding them wherever possible. In order to avoid using expensive and hard to find proprietary

memory, make sure any device you purchase accepts industry standard memory such as SD.

Fortunately, Sony’s newer devices are including support for industry standard SD memory formats in

response to the negative backlash against its proprietary Memory Stick.

ATA Flash PC Card

Although the PC Card (PCMCIA) form factor has been used for everything from game adapters to

modems, SCSI (Small Computer Systems Interface) cards, network cards, and more, its original use

was computer memory, as the old PCMCIA (Personal Computer Memory Card International

Association) acronym indicated.

Unlike normal RAM modules, PC Card memory acts like a disk drive, using the PCMCIA ATA (AT

Attachment) standard. PC Cards come in three thicknesses (Type I is 3.3mm, Type II is 5mm, and

Type III is 10.5mm), but all are 3.3-inch long by 2.13-inch wide. Type I and Type II cards are used

for ATA-compliant flash memory and the newest ATA-compliant hard disks. Type III cards are used

for older ATA-compliant hard disks; a Type III slot also can be used as two Type II slots.

xD-Picture Card

In July 2002, Olympus and Fujifilm, the major supporters of the SmartMedia flash memory standard

for digital cameras, announced the xD-Picture Card as a much smaller, more durable replacement for

SmartMedia. In addition to being about one-third the size of SmartMedia—making it the smallest

flash memory format yet—xD-Picture Card media has a faster controller to enable faster image


Both 16MB and 32MB cards (commonly packaged with cameras) record data at speeds of 1.3MBps,

whereas 64MB and larger cards record data at 3MBps. The read speed for all sizes is 5MBps. The

media is manufactured for Olympus and Fujifilm by Toshiba, and because xD-Picture media is

optimized for the differences in the cameras (Olympus’s media supports the panorama mode found in

some Olympus xD-Picture cameras, for example), you should buy media that’s the same brand as your

digital camera.

Just as with the proprietary Sony Memory Stick formats, I also recommend avoiding the proprietary

xD-Picture card format wherever possible. Instead, I only recommend purchasing devices that use

industry standard memory card formats such as SD. Because of the backlash against proprietary

formats, Olympus and Fujifilm abandoned xD-Picture card in 2010.

SSD (Solid-State Drive)

In general, a solid-state drive (SSD) is any drive using solid-state electronics (that is, no mechanical

parts or vacuum tubes). Many people believe that SSDs are a recent advancement in computer

technology, but in actuality they have been around in one form or another since the 1950s, well before

PCs even existed.

Today, solid-state drives are used for many of the tasks magnetic and optical drives have traditionally

performed, including system drives, primary and secondary data storage, and removable-media


Virtual SSD (RAMdisk)

Although most people think of a physical drive when they discuss SSDs, these drives are available in

both physical and virtual form. A virtual SSD is traditionally called a RAMdisk because it uses a

portion of system RAM to act as a disk drive. The benefits are incredible read/write performance (it

is RAM, after all), whereas the drawbacks are the fact that all data is lost when the system powers

down or reboots, and that the RAM used for the RAMdisk is unavailable for the operating system

(OS) and applications.

RAMdisk software has been available for PCs since right after the PC debuted in late 1981. IBM

included the source code to a RAMdisk program (later called VDISK.SYS) in the March 1983 PC

DOS 2.0 manual, as part of a tutorial for writing device drivers. (Device driver support was first

implemented in DOS 2.0.) IBM later released VDISK.SYS as part of PC DOS 3.0 in August 1984.

Microsoft first included a RAMdisk program (called RAMDRIVE.SYS) with MS-DOS 3.2 (released

in 1986). Versions of RAMDRIVE.SYS were included in DOS and Windows versions up to

Windows 3.1, and a renamed version called RAMDISK.SYS has been included with Windows XP

and Windows 7/Vista. However, they are not automatically installed, and they are not well

documented. These DOS- or Windows-based RAMdisk programs are useful for creating high-speed

SSDs using existing RAM. As an alternative to using RAMDRIVE.SYS, you can use a variety of

commercial and freeware utilities available for Windows and for Linux. (See

http://en.wikipedia.org/wiki/List_of_RAM_drive_software for links to some of these utilities.)

Flash-Based SSDs

Shortly after the release of the IBM PC in 1981, several companies developed and released physical

solid-state drives that could function as direct hard drive replacements. Many of these used

conventional dynamic or static RAM, with an optional battery for backup power, whereas others used

more exotic forms of nonvolatile memory, thus requiring no power to retain data. For example, Intel

had released “bubble” memory in the late 1970s, which was used in several SSD products. Bubble

memory was even included in the Grid Compass in 1982, one of the first laptops ever released.

Although SSDs can use any type of memory technology, when people think of modern SSDs, they

think of those using flash memory. Flash-based SSDs more recently started appearing in

commercially available laptop PCs from Dell, Asus, Lenovo, and others in 2007–2008. Since then,

many other laptop and desktop PC manufacturers have introduced systems with flash-based SSDs.

Ever since SSDs first became available for PCs in the early 1980s, many have thought that they

would universally replace hard drives. Well, it has been nearly 30 years since I first heard that

prediction, and it is just now becoming partially true. Until recently, the principle barriers preventing

SSDs from overtaking hard disks has been cost per GB and performance. Early SSDs were slower

than HDDs, especially when writing data, and performance would often fall dramatically as the drive

filled up. The development of controller hardware and operating systems optimized for SSDs have

enabled recent SSDs to surpass conventional hard disk drives in performance. Although SSDs are

still more expensive per GB than traditional hard disk drives, SSDs are now widely used for

applications where cost is not as important as performance and durability: Tablets, smartphones,

netbooks, and Ultrabooks use SSDs.

Many systems now strike a balance between the higher performance of SSDs and the greater capacity

of conventional hard disk drives by using both technologies. Many Ultrabooks use a small SSD

(32GB is a typical size) for the operating system and a conventional or hybrid SATA hard disk for

applications and system storage. Many high-performance desktop systems also use an SSD from

128GB to 512GB as a system drive, and a traditional hard disk for additional storage.


A hybrid SATA hard disk includes a small amount of flash memory used to cache mostfrequently-used information. To learn more, see Chapter 9.

Virtually all modern SSDs use the SATA (Serial ATA) interface to connect to the PC and appear just

like a standard hard disk to the system. Both 2.5-inch and 1.8-inch SSDs are shown in Figure 10.1.

Some high-performance SSDs come in a card-based form factor, usually designed for PCI Express


Figure 10.1. 2.5-inch and 1.8-inch solid-state drives (SSDs).

S LC Versus MLC

As previously mentioned, SSDs use NAND flash technology. Two subtypes of this technology are

used in commercially available SSDs: SLC (single-level cell) and MLC (multilevel cell). SLC flash

stores 1 bit in a single cell, whereas MLC stores 2 or more bits in a single cell. MLC doubles (or

more) the density, and consequently lowers the cost, but this comes at a penalty in performance and

usable life. SSDs are available using either technology, with SLC versions offering higher

performance, lower capacity, and higher cost. Most mainstream SSDs use MLC technology, whereas

more specialized high-end products (mostly for server or workstation systems) use SLC.

One major problem with flash memory is that it wears out. SLC flash cells are normally rated for

100,000 Write/Erase (W/E) cycles, whereas MLC flash cells are normally rated for only 10,000 W/E

cycles. When used to replace a standard hard drive, this becomes a problem because certain areas of

a hard drive are written to frequently, whereas other areas may be written to only a few times over

the life of the drive. To mitigate this wear, SSDs incorporate sophisticated wear-leveling algorithms

that essentially vary or rotate the usage of cells so that no single cell or group of cells is used more

than another. In addition, spare cells are provided to replace those that do wear out, thus extending

the life of the drive. Considering the usage patterns of various types of users, SSD drives are

generally designed to last at least 10 years under the most demanding use, and most last much longer

than that. As SSD capacity increases, so does the ability of the wear-leveling algorithm to spread out

data among available cells.

Note that, because of the way SSDs work internally, the concept of file fragmentation is immaterial,

and running a defragmenting program on an SSD does nothing except cause it to wear out sooner.

Unlike magnetic drives, which must move the heads to access data written to different physical areas

of the disk, an SSD can read data from different areas of memory without delay. The concept of the

location of a file becomes moot with wear leveling, in that even files that are presented as contiguous

to the file system are actually scattered randomly among the memory chips and cells in the SSD.

Because of this, SSDs should not be defragmented like traditional magnetic drives.


Windows 7 and 8 are SSD aware, which means they can tell an SSD from a standard magnetic

drive. These versions of Windows determine this information by querying the drive’s

rotational speed via the ATA IDENTIFY DEVICE command. (SSDs are designed to report

1rpm.) When Windows detects that an SSD is attached, it automatically turns off the

background Disk Defragmenter function, thus preserving drive endurance. When using SSDs

with Windows Vista and earlier versions, you should manually disable or otherwise prevent

any form of defragmentation program or operation from running on SSDs. For maximum

performance with any Windows version, install Tweak-SSD, available from


TRIM Command

Another technique to improve SSD endurance and performance is an extension to the ATA interface

called the TRIM command. This allows an SSD-aware OS (such as Windows 7 or later) to

intelligently inform the SSD which data blocks are no longer in use, thus allowing the drive’s internal

wear leveling and garbage collection routines much more space to work with, which allows the drive

to maintain a high level of performance especially after all blocks have been written to at least once.

For this to work, both the drive and the OS must support the TRIM command. Windows 7 and Server

2008 R2 and later are SSD aware and support the TRIM command, whereas earlier versions of

Windows do not. SSDs released in 2009 or later generally support the TRIM command, whereas

those that do not may be able to add support via a firmware upgrade. When you are upgrading the

firmware on an SSD, it is highly recommended to have a full backup because in some cases a

firmware upgrade reinitializes the drive, wiping all data in an instant.

When an OS deletes a file or otherwise erases data from a drive, it doesn’t actually erase data.

Instead, the OS simply marks the file allocation or master file tables to indicate that those blocks are

available, while leaving the data in them untouched. This works fine on a normal HDD because

overwriting is the same as writing, but it greatly hinders a flash drive since a flash drive cannot

overwrite data directly. On a flash drive, any overwriting causes the drive to first write any

previously existing data to a new block, then erase the block, and finally write the new data. Over

time, this results in the SSD filling up and slowing down, even though from the OS point of view there

is a lot of empty space.

When TRIM is used, whenever a file is deleted, copied, or moved or the drive is reformatted, the

drive is immediately informed of all the blocks that are no longer in use. This allows the drive

controller to erase the unused blocks in the background, ensuring that there is always a sufficient

supply of erased blocks available to keep write performance at near like-new levels.

To further improve SSD performance, Windows 7 and later disable features such as Superfetch and

ReadyBoost as well as prefetching on SSDs with random read, write, and flush performance above a

certain threshold.

When running a non-TRIM aware OS (Vista, XP, and earlier), you may still be able to take

advantage of TRIM by installing a TRIM-aware application. For example, Intel provides a program

called the Intel SSD Optimizer (part of the Intel SSD Toolbox) that you can periodically run to report

to the drive which files have been deleted. Other SSD manufacturers provide similar tools (often

called wiper.exe) as well. If you are running a non-TRIM aware OS with an SSD, check with the

SSD manufacturer to see if it has an optimization tool available.

Partition Alignment

Another issue with SSDs is that they are normally designed to read and write 4K pages and to erase

data in 512K blocks. Windows XP and earlier OSs normally start partitions 63 sectors into a disk,

which means that the OS file system components and clusters overlap pages and blocks, resulting in

more pages being read or written, and more blocks being erased than necessary, which can cause a

noticeable performance hit.

SSDs perform at their best when partitions are created with the SSD’s alignment needs in mind. All

the partition-creating tools in Windows 8/7/Vista place newly created partitions with the appropriate

alignment, with the first partition starting an even 2048 sectors into the disk. Because this is evenly

divisible by both 4K (8 sectors) and 512K (1024 sectors), there is no overlap between OS file

system cluster and SSD page/block operations.

Even if you are using Windows 8/7/Vista or another OS that normally creates aligned partitions, you

may still have misaligned partitions if the OS was installed into an existing partition or as an upgrade.

Many of the drive manufacturers have free partition alignment tools available that can check and even

correct the alignment of partitions on the fly. When creating new partitions on an SSD, you can

optionally use the DISKPART command to manually set the offset to the start of the first partition

such that all partitions on the drive will be properly aligned. With manual intervention, you can

ensure that even Windows XP and earlier will create partitions that are properly aligned for

maximum performance.

S S D Applications

SSDs are ideal for laptops because they are more rugged (no moving parts), weigh less, and consume

less power. The weight savings is fairly minor because the difference between an SSD and a

conventional drive of the same (or even greater) capacity is generally only a few grams. The power

savings is more real—SSDs only draw about a tenth of a watt compared to about 1 watt for an HDD

(average). But even that may be overstated. Although drawing one-tenth the power sounds like a

considerable savings, compared to other components such as the CPU, GPU, and display, each of

which draw 30 watts or more, the overall power savings in going from a standard HDD to an SSD is

relatively low in comparison to the total power consumed.

SSDs are ideal as the boot drive for desktop systems because of their performance. Using an SSD can

drop boot or resume from hibernation times dramatically. SSDs are less ideal for storing large

amounts of data because capacities are less than what is available for conventional HDDs.

Will your next computer contain an SSD? If you buy a tablet, a netbook, or an Ultrabook, the answer

is “very likely.” SSDs are big enough to contain the operating system and applications and are rapidly

dropping in price per GB compared to magnetic storage. Netbooks, Ultrabooks, and other PCs can

use external hard disk drives or cloud-based storage for data storage, and some Ultrabooks include

both a small SSD for use by Windows and a larger hybrid hard disk (magnetic storage with a small

amount of flash memory) for application and data storage. Tablets can use flash memory slots, cloudbased storage, or both to supplement the capacity of an SSD.

USB Flash Drives

As an alternative to floppy and Zip/SuperDisk-class removable-media drives, USB-based flash

memory devices have rapidly become the preferred way to move data between non-networked

systems. The first successful drive of this type—Trek’s ThumbDrive—was introduced in 2000, and

since then hundreds of others have been introduced.


Some USB flash memory drives are even built into watches, pens, bottle openers, and knives

(such as the Victorinox SwissMemory Swiss Army Knife).

Unlike other types of flash memory, USB flash drives don’t require a separate card reader; they can

be plugged into any USB port or hub. Any system running Windows XP or later can immediately

recognize, read from, and write to a USB flash drive. As with other types of flash memory, USB flash

drives are assigned a drive letter when connected to the computer. Most have capacities ranging from

2GB to 64GB, but can be as large as 256GB with even larger capacities planned for the near future.

Typical read/write performance of USB 1.1-compatible drives is about 1MBps. Hi-Speed USB 2.0

flash drives are much faster, providing read speeds ranging from 5MBps to 15MBps and write

speeds ranging from 5MBps to 13MBps. SuperSpeed USB (USB 3.0) flash memory drives are now

available for USB 3.0 ports common on most modern desktops and laptops. Although some USB 3.0

flash memory drives support read/write performance up to 150MBps, the actual interface is designed

to support up to 625MBps (5Gbps). As controllers improve, future USB 3.0 flash memory drives are

likely to provide performance closer to the maximum speed of the interface. Because Hi-Speed and

SuperSpeed USB USB flash drives vary in performance, be sure to check the specific read/write

speeds for the drives you are considering before you purchase one.


Q. Does my computer support USB 3.0? How can I tell?

A. USB 3.0 ports use blue connectors and are typically marked with an SS next to the USB fork

icon. In Windows Device Manager, look for an eXtensible Host Controller Interface (XHCI)

controller entry in the Universal Serial Bus category.

Q. Will my new 32GB SupersSpeed USB thumbdrive run at SuperSpeed or HighSpeed if I use

2.0 ports?

A. A USB 3.0 drive must be connected to a USB 3.0 port to run at SuperSpeed (5Gbps). If a

USB 3.0 drive is connected to a USB 2.0 port, it runs at USB 2.0 speeds (HighSpeed



If you have a card reader or scanner plugged into a USB hub or port on your computer, you

might need to disconnect it before you can attach a USB flash drive. This is sometimes

necessary because of conflicts between the drivers used by some devices. If you suspect this

type of problem, use the Windows Safely Remove Hardware icon in the system tray to stop the

card reader before you insert the USB flash drive. After the system has recognized the USB

flash drive, you should be able to reattach the card reader.

For additional protection of your data, some USB flash drives have a mechanical write-protect

switch. Others include or support password-protected data encryption as an option, and most are

capable of being a bootable device (if supported in the BIOS). Some drives feature biometric

security—your fingerprint is the key to using the contents of the drive—whereas others include more

traditional security software.

Some companies have produced bare USB flash drives that act as readers for MMC, SD, xD-Picture

Card, Compact Flash, and Memory Stick flash memory cards. These USB flash readers are

essentially USB flash drives without flash memory storage onboard. You can use them as a card

reader or as a USB drive with removable storage.

Comparing Flash Memory Devices

As with any storage issue, you must compare each product’s features to your needs. You should check

the following issues before purchasing flash memory-based devices:

• Which flash memory products does your camera or other device support? Although adapters

allow some interchange of the various types of flash memory devices, for best results, you

should stick with the flash memory type your device was designed to use.

• Which capacities does your device support? Flash memory devices are available in everincreasing capacities, but not every device can handle the higher-capacity devices. Check the

device and flash memory card’s websites for compatibility information. In some cases,

firmware updates can improve a device’s compatibility with larger or faster flash memory card


• Are some flash memory devices better than others? Some manufacturers have added

improvements to the basic requirements for the flash memory device, such as faster write

speeds and embedded security. Note that these features usually are designed for use with

particular digital cameras only. Don’t spend the additional money on enhanced features if your

camera or other device can’t use those features.

Only ATA Flash cards can be attached directly to an older laptop computer’s PC Card slot. All other

devices need their own socket or some type of adapter to transfer data. Figure 10.2 shows how the

most common types of flash memory cards compare in size to each other and to a penny.

Figure 10.2. SmartMedia, CompactFlash, MultiMediaCard, Secure Digital, xD-Picture Card,

and Sony Memory Stick flash memory devices. Shown in relative scale to a U.S. penny (lower


Table 10.2 provides an overview of the major types of flash memory devices and their currently

available maximum capacities.

Table 10.2. Flash Memory Card Capacities

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Chapter 10. Flash and Removable Storage

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