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I've happily installed Linux on my MacBook Pro with 4 GB of RAM, but I only get 3.6 GB available:

robert@raptor ~$ free -m
             total       used       free     shared    buffers     cached
Mem:          3684       2184       1500          0         83       1096
-/+ buffers/cache:       1004       2680
Swap:         6149          0       6149

I'm running a 64-bit kernel so this should not be a problem:

robert@raptor ~$ uname -a
Linux raptor #1 SMP PREEMPT 2010-10-25 08:40:12 +0200 x86_64 x86_64 x86_64 GNU/Linux

What can I do to get the whole 4GB available?

Update: this is what I get when running top on MacOS X:

PhysMem: 540M wired, 640M active, 231M inactive, 1411M used, 2685M free.

where used + free = 4096 MB.

Update 2: There's a thread on where a user complains of the same problem with Windows 7/64 bit.

Update 3: /proc/meminfo output:

MemTotal:        3773288 kB
MemFree:         1164244 kB
Buffers:          109096 kB
Cached:          1270520 kB
SwapCached:            0 kB
Active:          1446756 kB
Inactive:         962728 kB
Active(anon):     803404 kB
Inactive(anon):   230556 kB
Active(file):     643352 kB
Inactive(file):   732172 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:       6297596 kB
SwapFree:        6297596 kB
Dirty:               792 kB
Writeback:             0 kB
AnonPages:       1029880 kB
Mapped:           185096 kB
Shmem:              4096 kB
Slab:             131260 kB
SReclaimable:     106212 kB
SUnreclaim:        25048 kB
KernelStack:        2680 kB
PageTables:        21248 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     8184240 kB
Committed_AS:    3113016 kB
VmallocTotal:   34359738367 kB
VmallocUsed:      123884 kB
VmallocChunk:   34359596028 kB
HardwareCorrupted:     0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:       54444 kB
DirectMap2M:     3852288 kB

Memory info from dmesg:

[    0.000000] Memory: 3759972k/5242880k available (4780k kernel code, 1336600k absent, 146308k reserved, 6603k data, 892k init)

Update 4:

Video card info according to lspci:

02:00.0 VGA compatible controller: nVidia Corporation G96 [GeForce 9600M GT] (rev a1)

Some dmesg output related to the model:

[    0.000000] DMI: Apple Inc. MacBookPro5,3/Mac-F22587C8, BIOS    MBP53.88Z.00AC.B03.0906151647 06/15/09
share|improve this question
what does cat /proc/meminfo give? some kernels need patches on some hardware, have to deal with this at work sometimes, but we have special patches. – madmaze Nov 29 '10 at 17:41
My first thought was video memory, but apparently that's not it. In the kernel logs (typically in /var/log/kern.log or thereabouts depending on your distribution), there should be a line containing Memory: 1234567k/1236789k available …: what does it say? (If there are other memory-related lines nearby, post them as well.) – Gilles Nov 30 '10 at 1:17
@madmaze, @Giles: please see my update to the question – Robert Munteanu Nov 30 '10 at 7:55
hmm odd, I wonder if it has to do with the 1000 vs 1024 thing and OSx just pretends that it actually has 4GB. That is just a guess though. – madmaze Nov 30 '10 at 17:06
@madmaze : I'd be suprised if that was the case. OS X is certified Unix after all. – Robert Munteanu Dec 17 '10 at 16:13

try adding the kernel-PAE and kernel-PAE-devel packages to your linux installation. Then in grub select the entry to boot the PAE kernel, and see if you're still only seeing 3.6GB.

share|improve this answer
Thanks for the reply. I am currently using the -desktop kernel in OpenSUSE which contains PAE capabilities. But that is a non-issue since I am running the 64-bit variant : Linux raptor #1 SMP PREEMPT 2011-02-21 10:34:10 +0100 x86_64 x86_64 x86_64 GNU/Linux – Robert Munteanu Apr 26 '11 at 6:49

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