Hi, On Wed, Sep 8, 2010 at 12:12 PM, Teresa e Junior <teresaejun...@gmail.com> wrote: > But due to some features I need (not the eyecandy), I noticed the CD > only boots without gfx support (which is the most important for me).
You can't really safely use graphics support in a Live-CD anyway. GRUB and Linux use "video mode numbers" to request a video mode. These video mode numbers can be different for different video cards. Early versions of VBE did define some standard mode numbers, but these became obsolete in VBE version 2.0 (back in 1994). Software written after 1994 shouldn't rely on these obsolete video mode numbers. For example, if you're lucky mode 0x118 might be 1024*768 with 24-BPP, but nothing guarantees that anymore, and it could easily be any other video mode. There's also no guarantee that the the video card supports the video mode (e.g. a lot of video cards only support 32-BPP video modes and don't support any 24-BPP video modes; and some only support 24-BPP video modes and not 32-BPP video modes; and the same is true for 15-BPP vs. 16-BPP). Finally, even if you're lucky and VBE does support the video mode (and it's the right one, not something else); there's no guarantee that the monitor also supports the video mode (neither VBE nor GRUB nor Linux bother the check the monitors EDID information to make sure). This can be worse than "user can't see anything. For some (very old) "VGA only" monitors exceeding the monitor's maximum timing frequencies can cause the monitor to blow up (but these are quite rare now, for obvious reasons). I've also heard rumours that for some LCDs built into cheaper notebook type devices, exceeding the screen's maximum timing frequencies can cause permanent damage. Basically, the entire thing only works when the user tells GRUB/Linux which video mode to use (and then it's the user's fault if they choose something that doesn't work). It fails for a Live-CD which is meant to work "as is" and isn't pre-configured by the user. The only "least likely to fail" option would be to use standard VGA video modes instead - e..g mode 0x12 (320*200*256 colours) or mode 0x13 (640*480*16 colours). These mode numbers are "guaranteed" (by VGA compatibility) to be what you asked for, and are also "guaranteed" to work with the monitor (by VGA compatibility for older monitors and by VESA's "Safe Mode Timing" specification for newer monitors). Unfortunately they also suck - very low resolution and/or poor colour depth. Of course, I'm not saying that you can't unsafely use graphics support in a Live-CD - I'm sure plenty of people have done worse. Cheers, Brendan _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org http://lists.gnu.org/mailman/listinfo/grub-devel
