96 GB RAM on a Dell T7500 showing up as 78GB in Ubuntu Server 11.04
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?
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.