If the user has an EGA adapter, it may simply be incompatible with
SCO XENIX. Also it is possible that the switches on the EGA are
set incorrectly. If the card has an AUTOSWITCH feature, it must
be turned off. The user should also experiment with the
If the user has a VGA adapter, and is running an operating system
prior to SCO XENIX Release 2.2.3, the adapter will not work
regardless of what graphics mode it is set to. Only the Compaq VGA
is supported under SCO XENIX Release 2.2.3, and then only under EGA
mode. There is a Support Level Supplement that provides EGA support
for the IBM and Olivetti VGA cards running SCO XENIX Release 2.2.3.
If you have SCO XENIX 386 Operating System, request SLS xnx086. If
you have SCO XENIX 286 Operating System Release 2.2 and above, re-
quest SLS xnx084. These SLS's contain a new set of N volumes.
It is sometimes confusing to users how it could be a video card
problem when the 'boot colon' prompt is printed correctly. The
reason that this can succeed, while the boot up sequence fails,
is that up until a certain point the /boot program is using bios
calls to print out the information that appears on the screen.
At that point, the kernel is completely loaded and is then
invoked. Console output is then done under the control of the
kernel console device driver. The driver expects certain
behavior from the card. The video cards listed in the Release
Notes conform to the behavior that the device driver expects.
The point at which the kernel takes over console output using the
console driver is easily observed.
For SCO XENIX, at the boot: prompt, type:
boot: xenix prompt="Now switching--press RETURN"
For SCO UNIX, at the boot: prompt, type:
boot: unix prompt="Now switching--press RETURN"
If, upon booting, the above prompt is printed and the screen
clears or exhibits other abnormal behavior when <Return> is
pressed, then the problem is occurring at the exact point at
which the kernel takes over the hardware. This would imply a
video card incompatibility.
The Release Notes for the version of SCO XENIX or SCO UNIX System
V/386 that is installed.