Specifications

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For systems used for implementation into embedded solutions (Windows CE) there is no
such problem, systems do not write on the disk during work and if they need to write some-
thing, it is possible to create a virtual disk in RAM. Systems adapted for work in embedded
applications (Windows NT/XP Embedded) are equipped with a so-called write filter, which
is a component able to catch attempts to write to the hard disk and to prevent damaging
the FLASH memory. Ability to work without the page file is part of the modifications of the
system.
Although Windows NT Workstation 4.0 Embedded can be used in embedded solutions,
it was introduced on to the market just before the introduction of Windows 2000 on PC
and servers. Work on Windows 2000 Embedded started, but it was not introduced on to
the market. The final introduction was the version Windows XP Embedded (also called
Windows XPe).
Windows XPe (like Windows CE) is not sold as a product for end users. Only original
equipment manufacturers (OEM) may purchase development tools and create installation
Windows XPe for their equipment. There is a wide database of device drivers (graphic
adapters, network cards, printers, . . .) available. At the same time, there is available a
write filter for installation of the system on FLASH disks or for creation of a bootable
image of the system on CD-ROM (of course, Windows XPe may work from a standard hard
disk or boot the system from the network).
Writing data to CF card in Windows XP Embedded
When the Windows XPe operating system is installed on CF card, all writes to CF card
are stored to RAM buffer instead of directly to the CF card to protect the CF card from
“wearing off” (number of writes is limited to approx. 1 million). RAM buffers are physically
transferred to the CF card upon execution of the
ewfmgr command.
DataLab PC with Windows XPe pre-installed are supplied with a shortcut on the desktop,
which executes command
ewfmgr c : -commit. All data stored in RAM buffers are
passed to the file system to be written to the CF. However, keep in mind that the actual
write is performed during correct system shutdown or reboot. Simply switching the
computer off discards all writes.
It is necessary to keep this on mind when designing the embedded application and
when choosing the software platform and used utilities etc. Frequent stores should be
performed e.g. on remote disk storage. Another possibility is to use separate IDE Flash
disk or HDD for storing files. The CF card can be used for occasional writes (configuration
data etc.) without problems, just every change must be explicitly committed.
DataLab PC equipped with CF card can be switched off anytime without the risk of
corrupting the operating system or application files.