The tool SuperProbe is part of XFree86 and is able to check many graphic chips. Please read the documentation carefully, because it might crash your hardware. From man SuperProbe:
"SuperProbe is a program that will attempt to determine the type of video hardware installed in an EISA/ISA/VLB-bus system by checking for known registers in various combinations at various locations (MicroChannel and PCI machines may not be fully supported; many work with the use of the -no_bios option). This is an error-prone process, especially on UNIX (which usually has a lot more esoteric hardware installed than MS-DOS system do), so SuperProbe may likely need help from the user.
At this time, SuperProbe can identify MDA, Hercules, CGA, MCGA, EGA, VGA, and an entire horde of SVGA chipsets (see the -info option, below). It can also identify several HiColor/True-color RAMDACs in use on SVGA boards, and the amount of video memory installed (for many chipsets). It can identify 8514/A and some derivatives, but not XGA, or PGC (although the author intends to add those capabilities). Nor can it identify other esoteric video hardware (like Targa, TIGA, or Microfield boards).":
For testing reasons start the X11 server with X 2> <error.msg>. And try to change the resolution by typing <CTL><ALT><+> or <CTL><ALT><->. Note: the + or - sign have to be taken from the numeric pad, which can be emulated at the letter pad by some laptops.
Just watch the display and determine if it works properly. If not, try to enable different video modes at startup time. Setting up X11 can sometimes be an exercise in trial and error.
XFree86-HOWTO
XFree86-Video-Timings-HOWTO
XFree86-XInside-HOWTO
X-Big-Cursor-mini-HOWTO (useful when running X11 on a notebook with low contrast LCD)
Keyboard-and-Console-HOWTO
vesafb-mini-HOWTO
Framebuffer-HOWTO
You might discover that some features of your laptop are not supported by XFree86, e.g. high resolutions, accelerated X or an external monitor. Therefore I give a survey of available X11 servers.
XFree86 http://www.xfree86.org
VESA Frame-Buffer-Device, available with 2.2.x kernels and XFree86 3.3.2 or greater. http://linux-fbdev.org/ http://www.strusel007.de/linux/fb.html and kernel source /usr/src/linux/Documentation
Xinside also known as AcceleratedX http://www.xig.com , commercial
SciTech http://www.scitechsoft.com , commercial
Metro-X at http://www.metrolink.com, commercial .
If you can't get an appropriate X11 server working, but don't want to effort a commercial X11 server you may try the VGA16 or the mono server included in XFree86.
You may find a survey about X Windows resources at Kenneth E. Harker's page Linux on Laptops and a survey about current graphic chips used in laptops at MobiliX.
There are several different methods to activate support for an external monitor: as a BIOS option or during runtime with a keystroke e.g. <Fn>+<F4>.
Read the X11 docs about your graphic chip carefully, for instance for the NeoMagic NM20xx chips you have to edit /etc/XF86Config by configuring intern_disp and extern_disp. Note: As far as I know these options are only valid for XFree86 3.3.x, for XFree86 4.x I couldn't find a similar option.
If you can't get the external monitor to work with XFree86, try a demo version of the commercial X11 servers mentioned above. Also check with the RedHat and SuSE WWW sites as they may have new, binary-only, X11 servers that may work with your laptop.
Sometimes you may encounter a display not working properly in text mode. Currently I don't have any recommendations, please see Keyboard-Console-HOWTO.
Take care of the backlight as far as I know this device can only bear a limited number of uptime circles. So avoid using screensavers too much.
For problems with X Windows and APM please see the APM chapter.