In XFree86 CVS, the vesa driver appears to be doing portIO
to legacy vga registers. This makes things complicated because
these registers are shared between the primary and secondary
cards, and it places a large burden upon XFree86's RAC code
to make sure these registers are routed to the correct card
at the correct time.
My guess is that either the RAC code didn't handle this correctly
back in 4.0.2 or the vesa driver was doing something that
it shouldn't. The corruption you are describing actually
sounds like the vesa driver tried to restore the console
fonts, something it shouldn't have done if it was the
secondary card. Actually, looking at the vesa driver in
CVS it's not immediately obvious to me that it isn't trying
to restore the fonts on secondary cards. These are stored
in the first 64K or so of the framebuffer. If you've built
from source you could try commenting the font restoration
stuff out in the vesa driver to make sure it's not doing that.
If you have an option in your system bios to switch
which card is the primary, you might try that. Both the
"nv" and "nvidia" drivers should work OK on secondary
cards, but with the "nvidia" drivers you may need to be
running the very latest drivers and may need option "UseInt10Module"
to get it to post properly.
I don't know why 4.1.0 isn't working for you. Was that only
when trying with a two card setup?
Mark.
On Sun, 30 Dec 2001, erik vogan wrote:
> hello,
>
> i recently set up a dual head system running a 17" sony at
> 1280x1024x32 bpp off an nVidia GeForce2 GTS ("screen AGP") and a 14"
> dell monitor at 800x600x16 bpp off an ancient scavenged Diamond Stealth
> 64 VRAM (2 MB) ("screen PCI")
> [ XF86Config / XFree86.0.log at end of message ].
>
> configuration under 4.0.2 was pretty simply, and the system came
> up and functioned (quite a shock at first). i upgraded KDE to 2.2.2
> to allow me to use the extra screen real estate, and KDM came up fine
> (background on both screens). upon logging a user into KWM, however,
> the second screen blanked to the standard X hatch, then "screen AGP"
> showed my KDE background with display artifacts across the top 30 lines
> or so. attempting to move the cursor onto "screen PCI" (to the right)
> caused these display artifacts to saturate the top 30 lines or so of
> "screen AGP". pulling up a terminal window and entering "xset s reset"
> (found in the xpert archives) corrected the problem.
>
> it seemed every time the screensaver kicked on the same fix ("xset
> s reset") was required. some playing with xset allowed me to reproduce
> the problem with "xset dpms force suspend". i've paired the xset code
> down to minimal "break" and "fix" cases this afternoon. basically,
> the offending lines are:
>
> break:
> DPMSForceLevel(display, DPMSModeSuspend);
>
> fix:
> XResetScreenSaver(display);
>
>
> commenting out 'OPTION "DPMS"' in XF86Config fully corrected the
> situation with respect to both login and coming back from the screensaver.
>
> conclusion 1: my Dell 14" monitor (circa 1992) does not do DPMS
> conclusion 2: Xfree86 4.0.2 has a bug in how it deals with DPMS
> with regard to multiheaded mixed-DPMS systems.
>
> this is just gross speculation, but it appears that X is somehow
> mapping the display memory (or a portion of it) for "screen PCI" onto
> the base of the display memory for "screen AGP" after DPMS is
> engaged. XResetScreenSaver somehow modifies this behaviour.
>
> NOTE: before i played with the xset code i attempted to upgrade
> to xfree 4.1.0, but i got nothing from KWM past the background on
> "screen AGP" (no kpanel at the bottom of "screen AGP"), so no term window
> to check the "xset s reset" fix. that was before i disabled DPMS,
> and i haven't tried 4.1.0 again since i modified my setup to exclude DPMS.
>
> any suggestions on where to look / what to do in order to patch the
> code to allow DPMS on the screen that supports it ? any ideas why 4.1.0
> was such an impressive failure ?
>
> thanks for any pointers.
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