From: Jon Smirl <jonsmirl@yahoo.com>
To: Antonino Daplas <adaplas@pol.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>,
James Simmons <jsimmons@infradead.org>,
Linux Fbdev development list
<linux-fbdev-devel@lists.sourceforge.net>
Subject: Re: Reading the EDID block for x86 machines
Date: Mon, 17 Mar 2003 14:02:15 -0800 (PST) [thread overview]
Message-ID: <20030317220215.49788.qmail@web14902.mail.yahoo.com> (raw)
In-Reply-To: <1047933906.3668.18.camel@localhost.localdomain>
The VBIOS should be position independent code and it
will run at any 64K boundary. The PC bus spec simply
says the video BIOS defaults to C000, it is not a
requirement that it be located there. For example if
you look at the aty128fb driver's find ROM routine
your will notice that it is searching a broad address
space for the ROM.
I'm still not convinced that the memory at C000 is
really hardware write protected, I think it is just
RAM with a copy of the ROM in it. For example if I
turn off BIOS shadowing my system will not boot. When
debugging this I spent some time tracing into the ATI
ROM and I was pretty sure that they are dependent on
begin copied into RAM before begin run.
Do you have a DOS floppy around? Just boot into DOS,
start debug and see if you can change C000:0.
If C000:0 is hardware write protected, there is
nothing stopping the ROM from begin copied into 8000:0
or 9000:0 or whatever where there is guaranteed RAM.
We would just need to temporarily get the kernel out
of the way.
=====
Jon Smirl
jonsmirl@yahoo.com
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next prev parent reply other threads:[~2003-03-17 22:02 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-03-11 12:49 Reading the EDID block for x86 machines Antonino Daplas
2003-03-11 15:49 ` James Simmons
2003-03-11 20:07 ` Antonino Daplas
2003-03-11 21:33 ` Antonino Daplas
2003-03-11 21:47 ` Antonino Daplas
2003-03-11 22:05 ` Jon Smirl
2003-03-11 22:33 ` Antonino Daplas
2003-03-11 22:54 ` Jon Smirl
2003-03-11 23:02 ` Antonino Daplas
2003-03-11 23:42 ` Jon Smirl
2003-03-12 17:38 ` Antonino Daplas
2003-03-12 18:16 ` Jon Smirl
2003-03-12 22:38 ` Antonino Daplas
2003-03-12 23:36 ` Jon Smirl
2003-03-12 23:47 ` Jon Smirl
2003-03-13 6:50 ` Geert Uytterhoeven
2003-03-13 15:42 ` Jon Smirl
2003-03-16 23:00 ` Antonino Daplas
2003-03-17 4:00 ` Jon Smirl
2003-03-17 7:00 ` Antonino Daplas
2003-03-17 19:33 ` Jon Smirl
2003-03-17 21:38 ` Antonino Daplas
2003-03-17 22:02 ` Jon Smirl [this message]
2003-03-17 22:29 ` Antonino Daplas
2003-03-17 23:41 ` Jon Smirl
2003-03-18 9:06 ` Geert Uytterhoeven
2003-03-18 10:00 ` Antonino Daplas
2003-03-18 17:07 ` Jon Smirl
2003-03-19 5:15 ` Antonino Daplas
2003-03-19 6:07 ` Jon Smirl
2003-03-18 0:00 ` Jon Smirl
2003-03-11 23:54 ` Jon Smirl
2003-03-12 12:10 ` Ville Syrjälä
2003-03-12 17:38 ` Antonino Daplas
2003-03-12 18:47 ` Ville Syrjälä
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