determine the amout of video ram

[Kevin Freeman]

On Thu, 2003-12-11 at 15:41, Yohann Desquerre wrote:

> How is it possible that windows see 64Mo and the system see 504M0 (64 +
> 504 give a strange result whereas i have just 512 Mo plug into the box
> !!! 

The only reasonable answer is that the Windows driver is reporting an
incorrect number.  Since you know your system has 512MB RAM, and Windows
(and presumably Linux) report 504MB system memory available, then there
must only be 8MB allocated for video RAM.  i.e. 504+8=512.

However, 8MB is more than enough for your desired display resolution of
1152x864x24, and since that resolution works in Windows it will also
work in Linux ... unless there is a driver bug for that particular
graphics chip.

I assume you have verified the graphics chip and monitor were detected
by redhat-config-xfree86.  Now you need to verify the settings in
/etc/X11/XF86Config.  Since redhat-config-xfree86 has been "dumbed-down"
you will have to do this via a text editor.

Start by making a backup copy of /etc/X11/XF86Config:
  user at host ]# cp /etc/X11/XF86Config /etc/X11/XF86Config.backup

Now you have a way to return to your current settings in case of error
in the next steps.

Open /etc/X11/XF86Config in your favorite editor.  Near the bottom of
the file locate the Monitor section.  It should be similar to this:

Section "Monitor"
        Identifier   "Monitor0"
        VendorName   "Monitor Vendor"
        ModelName    "S/T 77E/76E"
        DisplaySize  320        240
        HorizSync    30.0 - 70.0
        VertRefresh  50.0 - 160.0
        Option      "dpms"
EndSection
                                                                                                                         Verify that the lines HorizSync and VertRefresh are within the specifications for your monitor.  If your documentation is unavailable you may be able to locate specifications on the web.  As a last resort use HorizSync 30.0 - 33.0 and VertRefresh  60.0 - 60.0, although this will not allow for your desired resolution.  The other lines in this section are unimportant and should be left alone - definitely do not change the Identifier value if it differs from above.  HorizSync and VertRefresh must be defined correctly!  Values outside the range of your monitor could lead to permanent monitor damage.

Next, locate the Screen section.  It should be similar to this:
Section "Screen"
        Identifier "Screen0"
        Device     "Videocard0"
        Monitor    "Monitor0"
        DefaultDepth     24
        SubSection "Display"
                Depth     16
                Modes    "1152x864" "800x600" "640x480"
        EndSubSection
        SubSection "Display"
                Depth     24
                Modes    "1152x864" "1024x768" "800x600" "640x480"
        EndSubSection
EndSection

DefaultDepth 24 specifies a default screen depth of 24 bits.  Safe
values for this setting are 24 and 8.  16 is usually safe, but some
graphics chips implement a 15-bit mode instead of 16-bit.  Your Windows
display properties should tell you whether your chip supports 15 or
16-bit.

Note also that there is a SubSection for each screen depth you wish to
use.  The above example only allows for screen depths of 16 and 24
bits.  To allow 8-bit screen depths, just add a SubSection with Depth
8.  The setting "Modes" in each SubSection specifies the allowable
display resolutions for each screen depth.  The Modes are entered in
decreasing order of preference - i.e. 1152x864 is the preferred
resolution in the above examples.

The Modes defined above are best thought of as "wishes."  You can enter
any exotic screen size you wish on the Modes line, but XFree86 will only
allow valid modes to be displayed.  XFree86 validates the mode "wish"
against the HorizSync and VertRefresh limits defined in the previous
Monitor section.  So just because you might have 1152x864 listed in both
16 and 24-bit SubSections does not mean that you can actually use that
resolution.

That was fun!  Now save the file.  If you are logged into X, log out. 
When you see the graphical login prompt, press <CTRL>-<ALT>-<Backspace>
(that's Backspace, not DEL) to completely reset the XFree86 subsystem. 
Log in and if all went well the screen will be at your preferred size
and depth.

If X refuses to start then you can restore the previously-working copy
of XFree86Config that you made earlier.

Hope this helps!
Kevin Freeman