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DL380 G4 and 4gig RAM, "missing" 512mb

Nick Gustafson
Occasional Contributor

DL380 G4 and 4gig RAM, "missing" 512mb

We have a couple of DL380's G3 and G4 machines in which we have upgraded the RAM to 4gig in each (4x 1Gig sticks). The G3 systems are working perfectly, but the G4 systems all report 3.5 gig of RAM to the OS instead of 4 gig. POST reports 4gig of ram, but the OS is only able to see 3.5 gig. We are running RHEL3 and Fedora Core 3 Linux installations on the systems. We have been through all the BIOS settings and don't see anything out of the ordinary. We have tried setting the memory to 4G in the Linux boot without success. Anyone else seen this or any suggestions?
John Marinov
Frequent Advisor

Re: DL380 G4 and 4gig RAM, "missing" 512mb

Update to latest firmware, at:


which says among other things (for the previous version)
Updated to resolve issue where systems with exactly 4 Gbytes of memory will not make all 4 GBytes available to the operating system. Typically, the system will report 3.5 Gbytes as being available
Respected Contributor

Re: DL380 G4 and 4gig RAM, "missing" 512mb

Normal Behaviour.

"Under the current memory addressing, there is a memory area just below 4.0 GB which is reserved permanently. The reserved area is for system BIOS to put APIC, ACPI Table, PCI Devices', Resources and AGP aperture information. When your systems memory is 3.5 GB or lower, the system will show that the same amount of memory has been implemented. However, if the system memeory is above 3.5 GB of memory, the actual amount of memory that the system shows will be less due to the reserved area. Regardless of memory size, the reserved memory addressing is always present, but only when the DRAM rises above the 3.5 GB amount will that area become visible."

See Microsoft for a resolution:;en-us;291988

Chaos, Panic or Disaster??? Always Stay Calm, I will fix it.
C. Beerse_1
Regular Advisor

Re: DL380 G4 and 4gig RAM, "missing" 512mb

If you installed the default kernel while having less than 4 GByte memory, you most-likely donnot have a big-memory kernel.

Hence, you might need to update the kernel to a kernel that is build for big-memory. `uname -r` on our RH9 system reports "...bigmem". On our RHEL3 system, it reports "...smp" (this appears to include big-memory). We also had systems that report something like "...enterprise" or such.

make everything as simple as possible, not simpler (A.Einstein??)