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Compact Flash (CF) Cards and Handheld PCs


Applies To

  • Windows CE 1.0, 1.01
  • Windows CE 2.0, SP1
  • Handheld PC Pro, SP1
  • Handheld PC 2000
  • Windows CE 4.0, 4.1, 4.2 .net


This article provides an overview of Compact Flash storage cards and discusses the technical constraints of using CF cards with Windows CE based Handheld PCs.


CF Cards or Compact Flash cards are the original generation of storage solutions with a mobile footprint.


CF Cards were an important step forward in mobile storage solutions. Unlike Hard drives they contain no mechanical parts and provide a constant, reliable non-volatile way of storing data without a power supply. Previous technologies used volatile memory technologies, requiring a constant power source to maintain data integrity.

The Compact Flash specification defines a Solid State (No moving parts), non-volatile (doesn't require any external component to maintain the integrity of the stored information i.e. a power supply). CF Cards run at either 3.3 or 5 volts, requiring less than 5% of the power needed by a small hard disk drive that operates within the PCMCIA specification.

One of the greatest features of CF cards is that they operate using the ATA / ATAPI specification as well as supporting the PCMCIA ATA specification. This means that CF Cards can operate using the same driver technology as Hard Disks and PCMCIA Storage solutions. Allowing CF cards to operate in a raft of devices, under a range of operating systems without the need for additional software.

The life span of a CF card with its built in defect management and error correction technologies stored data given normal use is roughly 100 years with no data deterioration. CF Cards can withstand falls equivalent to that of a 10ft (3 metres) drop.

Current day CF Cards range from sizes of 2MB up to specialist cards with 5,120MB (5GB) or more in capacity. CF Cards are a very cheap way to increase the storage capacity of your Handheld PC.


There are two versions of the Compact Flash Specification. The primary difference between the older type 1 specification and the newer type 2 is the data rate supported by the card. Type 1 cards support data transfer rates of 8MB/s where as Type 2 cards will support speeds of up to 16MB/s. The CF 2 specification is backward compatible with the type 1 specification but crucially Type 2 cards can be used with type one hardware at the slower transfer rate. Ensuring compatibility at least on the hardware level.

CF Specification

Bus Speed

Direct Memory Access

Compact Flash Type 1

8 MB/s


Compact Flash Type 2

16 MB/s


Compact Flash Type 3

66 MB/s


Whether a CF card is compatible with a particular device is down to the software which the device runs on. All digital media must conform to a File System specification. Examples of file systems are FAT, NTFS, Ext2, Ext3.

The most common and widely supported File System is the Microsoft FAT or File Allocation Table method. FAT is supported by virtually all operating systems. Unfortunately there are several sub specifications of the FAT specification. This is where complication can arise with supporting different sized CF cards.


FAT12 was introduced in MS-DOS 1.0. It is severely limited as it only supports Partitions of 8MB. Floppy disks are formatted to FAT12. Any CF Card formatted through DOS under 8MB in size will be formatted to FAT12. FAT12 is supported by all versions of Windows CE, as well as virtually any Operating System.


FAT16 was introduced in MS-DOS 3.0, but wasn't fully supported until the release of MS-DOS 4.0. FAT16 supports Partitions of up to 2GB (2,048MB). Most CF Cards will fall into this area. It is addressable by Windows CE and most Operating Systems. We do not recommend that you use CF Cards over 256MB with Windows CE 1.


FAT32 was introduced with MS-DOS 7.0 (Windows 95) and theoretically can support up to 32TB 32,000,000 MB. However is limited by Microsoft to supporting a maximum of 32GB. FAT32 can be accessed by Windows CE 2.11 and higher and generally only Microsoft Operating Systems.

Using a CF Card between a Handheld PC and another PC can be complicated by Windows NT. If you wish to use your CF card in Windows NT (Windows NT 3.51, NT 4.0, 2000, XP, 2003) you should not attempt to format your card using Disk Administrator or Windows Explorer.

Windows 2000, for example is able to support hard disk optimised File Systems running on the FAT specification beyond those supported by the original MS-DOS implementation. As a result of using more advanced cluster sizes Windows will automatically attempt to make the optimum use of your CF card. Handheld PC devices are only able to support the MS-DOS implementation of FAT.

While MS-DOS can only support a maximum FAT12 volume of 8MB, Windows 2000 can technically support a FAT12 volume of 32MB. While Windows 2000 has been programmed to format 32MB cards using FAT16, cards of sizes between 8MB and 16MB may be formatted using FAT12, rendering it unreadable by Windows CE.

The same may be true for CF Cards over 512MB which may be formatted to FAT32 by default. Cards over 2GB must be formatted to FAT32. By default Windows XP will format cards larger than 32MB as FAT32. As a result the following restrictions apply:

Windows CE 1

Recommended Maximum CF card size is 256MB although it should support cards of up to 2GB. HPC:Factor does not recommend the use of larger cards as CE 1 was never tested with large external storage cards.
Supports 8MB FAT12 and FAT16

Windows CE 2

Supports FAT12 up to 8MB as well as FAT16 volumes up to 2GB


Supports 8MB FAT12, FAT16 and FAT32 volumes up to 32GB


Supports 8MB FAT12, FAT16 and FAT32 volumes up to 32GB

Formatting a CF Card

Windows CE based Handheld PCs are able to format a CF card. However the Operating System has been limited to being able to format a card but only if it is unable to successfully read the volume. In such an event an image similar to the following will be displayed.
There are third party utilities that will allow you to format a CF card directly on the Handheld.

Format Storage Card Prompt

We recommend that you use MS-DOS or Windows 95 OSR2 / 98 / 98SE / Millennium to format the card in an external reader. Using DOS or Windows 9x will ensure that you maintain the correct File System standards.

Operating System Supported File Systems
MS-DOS 1 - 3 FAT12
MS-DOS 4 - 6.22 FAT12, FAT16
MS-DOS 7 - 8 FAT12, FAT16, FAT32
Windows 3.1x FAT12, FAT16
Windows NT 3.51 FAT12, FAT16 (NTFS, HPFS)
Windows 95 FAT12, FAT16
Windows 95 OSR2.x FAT12, FAT16, FAT32
Windows NT 4.0 FAT12, FAT16 (NTFS, HPFS up to SP3)
Windows 98 FAT12, FAT16, FAT32
Windows 98 SE FAT12, FAT16, FAT32
Windows 2000 FAT12, FAT16, FAT32 (NTFS)
Windows Millennium FAT12, FAT16, FAT32
Windows XP FAT12, FAT16, FAT32 (NTFS)
Windows Server 2003 FAT12, FAT16, FAT32 (NTFS)

You can use 2000, XP or 2003 to format the card however it may render the card unusable in Windows CE if not performed correctly.

To format a CF Card using MS-DOS or the command prompt:

At the command prompt type:

  1. format X:

Where X: is the drive letter assigned to your CF reader. Follow the instructions on the screen.

To format using Windows 95, 98, 98SE

  1. Open 'My Computer'
  2. Right click the Drive assigned to the CF Reader
  3. Select Format
  4. Select Full
  5. Click Start

To format using Windows 2000, XP, 2003

  1. Open 'My Computer'
  2. Right click the Drive assigned to the CF Reader
  3. Select Format
  4. Select the appropriate File System from the drop down list (Either FAT or FAT32)
  5. Select Default Allocation Size from the Allocation Unit Size drop box
  6. Ensure that Quick format and Compression are Disabled
  7. Click Start


CF Cards are the ideal way to expand the functionality of your Handheld PC by increasing it's memory. One feature of all Handheld PCs is the presence of at least one CF slot. Due to the hybrid standards used by CF, you can also use a PCMCIA adapter to add additional CF storage to your device.

For more information on using CF cards in your device see:

CESDH0013 - Using a CF Storage Card

For information on compatible CF Cards and other hardware devices for your Handheld PC please see the HPC:Factor Hardware Compatibility List.