I have two different kernels on my machine :

1. 2.4.20-8 (Vanilla kernel shipped with RH 9).
2. 2.4.21 (custom compiled kernel with acpi patch and IRQ's
allocated with ACPI).

The XF86Config being the same with both, I notice the following
behaviour :

1 - > Use of Fn-F7 allows me to switch between external monitor, external
monitor+own monitor and own monitor modes, as should be.

2. -> Use of Fn-F7 does nothing. If I boot with external monitor connected,
only the external monitor works, otherwise only the laptop's own monitor

I have heard that the BIOS sets this thing up in some fashion, but
since I use ACPI subsystem to assign IRQ's in the 2nd case, I presumably
cannot use that. Is there some way I could mimic the behaviour of
configuration 1 with configuration 2 ?