Devel Digest, Vol 34, Issue 1
wmb at laptop.org
Mon Dec 1 03:45:25 EST 2008
> 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.
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