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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.

Has anyone ever heard of this on a 64-bit kernel? I just don't quite understand what could be the issue.

10$ uname -a
Linux macbook 2.6.28-15-generic #49-Ubuntu SMP Tue Aug 18 19:25:34 UTC 2009 x86_64 GNU/Linux

$ free -m
             total       used       free     shared    buffers     cached
Mem:          2953       1031       1921          0        114        427
-/+ buffers/cache:        489       2463
Swap:         7812          0       7812

9$ lsmod
Module                  Size  Used by
i915                   77960  2 
drm                   123232  3 i915
binfmt_misc            18572  1 
ppdev                  16904  0 
btusb                  21784  2 
bridge                 63776  0 
stp                    11140  1 bridge
bnep                   22912  2 
vboxnetadp            109356  0 
vboxnetflt            116972  0 
vboxdrv              1721612  1 vboxnetflt
uvcvideo               69640  0 
compat_ioctl32         18304  1 uvcvideo
videodev               45184  2 uvcvideo,compat_ioctl32
v4l1_compat            23940  2 uvcvideo,videodev
lp                     19588  0 
parport                49584  2 ppdev,lp
snd_hda_intel         557492  3 
snd_pcm_oss            52352  0 
snd_mixer_oss          24960  1 snd_pcm_oss
snd_pcm                99464  2 snd_hda_intel,snd_pcm_oss
arc4                   10240  2 
snd_seq_dummy          11524  0 
ecb                    11392  2 
snd_seq_oss            41984  0 
snd_seq_midi           15744  0 
snd_rawmidi            33920  1 snd_seq_midi
snd_seq_midi_event     16512  2 snd_seq_oss,snd_seq_midi
snd_seq                66272  6 snd_seq_dummy,snd_seq_oss,snd_seq_midi,snd_seq_midi_event
ath9k                 310584  0 
snd_timer              34064  2 snd_pcm,snd_seq
snd_seq_device         16276  5 snd_seq_dummy,snd_seq_oss,snd_seq_midi,snd_rawmidi,snd_seq
mac80211              251528  1 ath9k
iTCO_wdt               21712  0 
iTCO_vendor_support    12420  1 iTCO_wdt
joydev                 20992  0 
video                  29204  0 
snd                    78920  15 snd_hda_intel,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_seq_oss,snd_rawmidi,snd_seq,snd_timer,snd_seq_device
applesmc               37700  0 
output                 11648  1 video
soundcore              16800  1 snd
pcspkr                 11136  0 
cfg80211               43680  1 mac80211
appletouch             19972  0 
isight_firmware        11520  0 
input_polldev          12688  1 applesmc
intel_agp              39408  1 
snd_page_alloc         18704  2 snd_hda_intel,snd_pcm
led_class              13064  2 ath9k,applesmc
hid_apple              15872  0 
usbhid                 47040  0 
ohci1394               42164  0 
ieee1394              108288  1 ohci1394
sky2                   63364  0 
fbcon                  49792  0 
tileblit               11264  1 fbcon
font                   17024  1 fbcon
bitblit                14464  1 fbcon
softcursor             10368  1 bitblit

Some information from dmesg:

[  795.820163] ACPI: EC: GPE storm detected, transactions will use polling mode
[ 1762.709516] [drm:i915_getparam] *ERROR* Unknown parameter 6
[ 1763.078130] [drm:i915_getparam] *ERROR* Unknown parameter 6
[ 2362.760889] [drm:i915_getparam] *ERROR* Unknown parameter 6
[ 2416.352084] ACPI: EC: missing confirmations, switch off interrupt mode.
[ 3718.721095] [drm:i915_getparam] *ERROR* Unknown parameter 6
[ 3719.108914] [drm:i915_getparam] *ERROR* Unknown parameter 6
[ 4318.773266] [drm:i915_getparam] *ERROR* Unknown parameter 6
[ 9513.813066] CE: hpet increasing min_delta_ns to 15000 nsec
[ 9693.815684] npviewer.bin[6736]
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migrated from stackoverflow.com Sep 26 '09 at 21:17

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3 Answers

up vote 3 down vote accepted

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 :-)

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Especially ironic since 32bit Linux will use >4Gb on most PCs (PAE gives you 36bit addressing) –  Martin Beckett Sep 26 '09 at 21:48
2  
With this chipset, the 3GB limit is the hardware limit... same thing goes to f.e. thinkpad x60 (which also got 945) -- your chipset simply will not handle 4GB, and this is not related to OS. –  liori Sep 26 '09 at 22:13
2  
mgb: It's not an address space issue. It's a physical address mapping issue. If your chipset does not support address remapping for 3GB-4GB space, no matter your OS is 32 bit or 64 bit, you can't access the amount of memory masked by I/O devices for MMIO use. –  LeakyCode Sep 26 '09 at 22:24
    
Damn... Thanks a lot for the responses. What about the laggy video? Is that due to a hardware conflict? While it sucks that I can't have 4GB, its nice to be getting some answers. –  user12453 Sep 27 '09 at 0:43
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The lagging video might be due to Intel GMA drivers which is known to have problems. Please do have a look at this thread on Ubuntu Forums.

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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"
    # ...
EndSection

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

Section "DRI"
    Mode 0666
EndSection

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

direct rendering: Yes
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Thanks for the info voyager! Unfortunately I believe the laggyness is caused by that 1GB overlap in memory allocation (as per the 945 chipset limitation). My video runs great with only 3GB. But I've got that link bookmarked, as I'm sure I'll eventually have driver issues with an upgrade. Thanks again! –  user12453 Sep 27 '09 at 16:48
    
You are welcome! –  voyager Sep 27 '09 at 19:40
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