Running Ubuntu Server 11.04. I've got a new Dell Precision T7500 workstation loaded up with 12x8GB DIMMs and the BIOS shows 96GB but checking /proc/meminfo gives:

cat /proc/meminfo | grep MemTotal
MemTotal:       82650584 kB

and free gives:

free -m
             total       used       free     shared    buffers     cached
Mem:         80713       5254      75459          0         89       3304
-/+ buffers/cache:       1860      78852
Swap:        95365          2      95363

The Win7 install that it came with showed 96GB with 80 GB usable, as well.

Does anybody know what's going on?

  • 5
    Please post the output of cat /var/log/dmesg | grep Memory – Zoredache Aug 29 '11 at 18:34
  • 1
    Ensure that you are running the latest BIOS update. I'm not saying that's your solution but it's probably a good starting point... – HTTP500 Aug 29 '11 at 19:29
  • What is the output of dmidecode -t 16 -t 17? – sciurus Aug 29 '11 at 20:09
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    cat /var/log/dmesg | grep Memory [ 0.000000] Memory: 82641428k/84672512k available (5510k kernel code, 788924k absent, 1242160k reserved, 3122k data, 812k init) – Ryan N Aug 29 '11 at 22:22
  • and the dmidecode: pastebin.com/axGdhXvq – Ryan N Aug 29 '11 at 22:24

Have you tried the kernel-parameter "mem=96G" ?


We're run into a few problems with RAM and/or Video memory addressing across a few iterations of Dell hardare where I work and found the solution to be adding pci=nommconf as a kernel option in grub - worth a try.


Are you using two CPUs? If this workstation got 18 slots and you're only getting use of 9 out of 12 memory sticks working. It almost sounds like you're only using 1 CPU. Other than that, there might be failure in your motherboard / firmware.


You need to change the Memory Mode in BIOS to "Optimizer" so all memory is available to the operating system.

Possible of memory mode selections:

  • Optimizer Mode — mode uses Independent channel configuration for highest memory subsystem performance. This is the default ordering configuration choice.
  • Advanced ECC Mode — RAS feature that extends multi-bit single device error correction to x8 DRAMs, which runs pairs of memory channels in lockstep mode. There can be a substantial hit to memory performance when using this mode.
  • Spare Mode — RAS feature that allocates one rank per channel as a spare to reduce the likelihood of correctable errors from becoming uncorrectable errors, but at a cost to memory capacity.
  • Mirror Mode — RAS feature with paired memory channels that provide data and transmission fault-tolerance, but available memory capacity is reduced by 50 percent and system memory bandwidth will decline.

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