Devel Digest, Vol 34, Issue 1

[Mitch Bradley]

>
> I am wondering if there is currently any possbility to completely turn
> off the whole video subsystem, while leaving the cpu running? [and is
> it also possible to "reclaim" the video RAM for the system BTW ?]
>   

Yes, it's possible, but I don't know if anybody has the recipe handy, 
especially not in the context of the existing OS setup.

To reclaim the video RAM, you would need to change the values in quite a 
few MSRs (machine specific registers).  There are about 6 of them whose 
values depend on the chosen size of video RAM - MSR numbers 10000028,  
10000029, 4000002a, 00001810, and a0002001.

Open Firmware sets that up and hands it off to Linux.  In principle, the 
Linux kernel could change the values after the fact, but it would be tricky.