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64-bit linux kernel only seeing 3 of 4GB after upgrade

64-bit linux kernel only seeing 3 of 4GB after upgrade

Hey everyone. I am running Ubuntu 9.04 64-bit on my macbook. I had 2GB of ram before, and everything ran great. I just upgraded to 2x2GB (4GB), but my system only sees 3GB of it. OS X, which I am dual booting, sees all 4GB. Also, my video performance is incredibly lacking. Before the upgrade my compiz benchmark was full at 80fps, and now it is at 22fps with very choppy window dragging.

Asked by: Guest | Views: 50
Total answers/comments: 2
Guest [Entry]

"If you have the Mac Books with Intel 945 Chipset, you can only use 3 GB. Mac OS ""About this Mac"" will show the total 4 GB, but the O/S will only be able to use 3 GB, just like Linux.

The Reason you are seeing 4 GB using ""About this Mac"" is because Mac OS X will take that value not from what is usable, but from what the DIMMs report while probing hardware.

And yes, this belongs-on-superuser :-)"
Guest [Entry]

"In regard to the video issue, try upgrading the kernel and reinstalling the video module for your chipset, Intel used to have great support for Linux. Also it could simply be that you got Direct Rendering Infrastructure disabled in an upgrade.
In point 5.3 of Intel's own page on Linux drivers is a walk through on how to enable it.

DRI (Direct Rendering Infrastructure) is a framework for allowing direct access to graphics hardware under the X Window System in a safe and efficient manner. You need enable DRI in xorg.conf.
Firstly, make sure the GLX and DRI modules are being loaded:

Section ""Module""
# ...
Load ""glx""
Load ""dri""
# ...

Then, set the permissions for DRI appropriately. To allow anyone to use DRI, do:

Section ""DRI""
Mode 0666

After restart X server, you can check whether direct rendering is enabled by running glxinfo, the output of glxinfo should show:

direct rendering: Yes"