On 5 Jun 00, at 5:40, Hal Trachtenberg wrote:

> An invalid page fault error is an error that occurs in upper memory . It is
> when a program tries to access a part of  that memory that is already in
> use. Upper memory begins at A0000 and goes through FFFFF. The first part of
> upper memory stores Video Rom and Ram, A0000 through CFFFF, which is the
> first 64k of upper memory, also called the PAGE FRAME. This frame is divided
> into 4 pages of 16k each. So when a program tries to access this memory area
> you get an invalid page fault. The address in the error that you got
> (bffxxxxx) indicates that Rundll32 tried to access the memory address
> assigned to video text and color Ram.
>
> Hal
> From: J & M Home Computer Services
>
> > When installing Windows98 se I get a fault saying - Rundll32 caused an
> > invalid page fault in module kernel32.dll at 0167:bff74347
> >
> > Can anyone give me an idea of what's causing this fault?
> >
> > Thank you,
> >
> > Michael Murray

  I'm afraid this answer is 5-10 years out of date.

  [For those that care:  The address ranges A0000-FFFFF are "upper
memory only in "real" mode (i.e., DOS), and their allocation for
video ROM and RAM is specific to this mode as well.  A0000-CFFFF is
192K, not 64K.
  The subdivision of a 64K segment into four 16K page frames was
typical of the EMS (Expanded Memory System) standard, originally
implemented in hardware for the 8088, and later often emulated in
software on 386 and higher CPUs.]

  In a virtual-memory mode, such as provided by the 386 and higher
CPUs, the virtual memory space is subdivided into "pages" which are
typically 4K in size.  [This size was common on mainframes in the
1970s and chosen by Intel when designing the 386; just as there have
been machines on which bytes were not 8 bits, there have been some on
which pages were not 4K.]
  Physical RAM is also subdivided into pages, and a special set of
memory-management registers keeps track of which 4K virtual page is
currently mapped to each 4K physical page.  [A few virtual pages are
"locked" to specific physical pages because they contain, for
instance, code for managing the page mapping....]

  A "fault" is an interrupt signal from the CPU hardware to the
operating system.  Specifically, a "page fault" indicates that some
instruction tried to access a virtual address on a page that does
not, at this moment, map to any physical page.  Normally, this will
be the OS's cue to try and free up a physical page (saving the
contents to the swap file if necessary) and load the needed page from
disk; when this is completed, the instruction which triggered the
fault signal can be retried and should now succeed.

  One of the ways in which a page fault could be "invalid" is if
there is no section of the swap file that maps to that virtual page,
either.  This is a little different from a protection fault, where
the target page exists but the code containing the instruction is
barred from accessing it in the desired fashion.  Of course, neither
of these should happen in well-written sofware under ordinary
circumstances, but reality is that when different pieces of software
have to work together, they don't always see eye-to-eye.

David G

                         PCSOFT's List Owner's:
                      Bob Wright<[log in to unmask]>
                       Drew Dunn<[log in to unmask]>