epia m vga + memcpy failed

Ronald G. Minnich rminnich at lanl.gov
Tue Sep 7 22:11:01 CEST 2004

On Wed, 8 Sep 2004, Peter Stuge wrote:

> On Tue, Sep 07, 2004 at 08:15:47PM -0400, Trellix78 at aol.com wrote:
> > That message is from the original freebios.  I was thinking that
> > shadowing is not corretly set up and that maybe the
> > segment is write-protected.  After setting up shadowing,
> > the chipset my turn on write protection by default, anyway.  I
> > don't know how to turn write protection off specifically for the
> > C00000 segment.  So far, the only reference that I can find about
> > write protection is in the Pentium developer's manual. It says to
> > have bit 16 of CR0 be zero to turn off write protection.
> That's controlled by the descriptor table flags for the particular
> descriptor in use. (cs/ds/es)

ah,well, sorta. 

There are north bridge issues. There are lots of ways in the x86 
architecture for writes to fail ...

> Trying to write to protected memory would cause a page fault that
> LB probably doesn't recover from. (Are PF:s handled at all?)

no, that's not necessarily the case ...


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