What is "nomodeset" SUPPOSED to do?

Tom Horsley horsley1953 at gmail.com
Tue Jun 1 01:30:52 UTC 2010

On Mon, 31 May 2010 20:04:53 -0500
Steven P. Ulrick wrote:

> What is "nomodeset" SUPPOSED to do?

The newest kernels have (God knows why) moved the video
mode setting into the kernel (the only explanation I've
ever seen for why this is a good idea is that the monitor
goes "click" less often that way). So all the programming
of the hardware specific clock rates and registers on the
video card happen in the kernel during initial boot
rather than in the X driver when the X server starts.
(And the X driver developers hate having to deal with
both possibilities, so they'd really like no one to ever
use nomodeset).

The "nomodeset" kernel parameter turns off this feature
and leaves the system BIOS video setting in place during

Because the kernel may need the video driver loaded to
do mode setting, the nouveau driver is probably included
in the initrd image, hence the need for both "nomodeset"
and "rdblacklist=nouveau" to keep the kernel out of the
video mode business so the binary nvidia driver can
then do mode setting when X starts with no conflicting
drivers loaded in the kernel.

That, at least, is my summary of the obscure bits of
information I've absorbed over time (maybe incorrectly)
about this mode setting issue.

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