Re: EWF and FBWF Newbie Questions
- From: "Sean Liming \(MVP\)" <sean_liming@xxxxxxxxxxxx>
- Date: Mon, 30 Jul 2007 07:29:05 -0700
Welcome to the operating system that works! ;)
XPE runs off sector based disk just like XP Pro does. Windows CE requires special drivers because it can execute in place (XIP) out of flash. With XP/XPe access to a disk is already built in.
XP/XPe contastantly access the disk, even when you are not doing anythin on the computer, this can wear down a flash disk. Wear-leveling has to be built into the disk level since it is not part of the operating systems. You will see many topics on booting XPe from flash disks; notably CF and USB flash disks. CF cards come in different flavors - some support wear-leveling many don't. http://www.seanliming.com/flashhelp.html.
EWF and FBWF can be used to protect the life of the flash, but can be controlled so you can still update the OS. They also provide protection in case of sudden power outage.
--
Regards,
Sean Liming
www.sjjmicro.com / www.seanliming.com
Book Author - XP Embedded Advanced, XP Embedded Supplemental Toolkit
"authorwjf" <authorwjf@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message news:382976FF-B2F6-48C9-B0C6-B3DF72189F73@xxxxxxxxxxxxxxxx
Hi All~
I am hoping someone out there will have time to answer a couple newbie
questions for me about EWF / FBWF from a conceptual standpoint. I am new to
XPe coming from the WINCE world.
In Windows CE, I worked on a number of flash based OS devices. These used
3rd party utilities to manage the flash RAM. In one case I used Intel's PSM
and in another a similar tool from Datalight. The idea was two fold. The
first was protection. We had a protected area of flash for a base OS image,
plus a semi-protected area for the registry (required explicit flushing to go
from RAM to the solid state media), and finally, a completely read/write
enabled area for user and application data.
I sort of see how EWF and especially FBWF can fill the bill here so to
speak. Though I am a little fuzzy on both the usage of a page file, and, the
RAM requirements for EWF (sounds like maybe you must have the same amount of
RAM as you do EWF protected flash space?). What I don't see is the second
purpose of the flash management in WinCE. By that I am talking about
low-level wear leveling on the media. What component or driver in XPe
prevents us from prematurely wearing out the flash, besides simply trying to
minimize writes to it? I don't see any "scatter write" functionality unless
I am missing something.
Thanks in advance to anyone who takes the time to answer my query. I know I
am probably asking very elementry questions at this point, but we all have to
start somewhere right? I did read the MSDN intros on both EWF and FBWF so
while I am all for links to other docs, unless I missed something I did not
see the answers to my questions there specifically.
~Bill
.
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