windows server 2012r only 64gb of 128gb of memory unable

We have a server Lenovo R540   and  upgrade to 128 GB   but in the property page shows 128GB   (64GB usable)
We need all me to be use by the SQL server which run couple of DB  for at least 20 users .
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Dean ChafeeIT/InfoSec ManagerCommented:
Perhaps the RAM was configured in a mirror configuration?  Not sure about Lenovo, but Dell has this option. If this is the case, it is typically changed in BIOS and/or physical RAM slots.
David Johnson, CD, MVPOwnerCommented:
What is the proper Server Version, IBM/Lenovo doesn't make an R540, Dell does make a Poweredge R540.

Single or Dual CPU? If Dual then you have to have equal amounts of ram for each cpu
Shaun VermaakTechnical SpecialistCommented:
What edition?

Version      Limit on X64

Windows Server 2012 Datacenter      4 TB
Windows Server 2012 Standard      4TB
Windows Server 2012 Essentials      64 GB
Windows Server 2012 Foundation      32 GB
Windows Storage Server 2012 Workgroup      32 GB
Windows Storage Server 2012 Standard      4 TB
Hyper-V Server 2012      4 TB

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MFAITAuthor Commented:
Ok  you answer me  thanks   We have essentials ...Any easy way to upgrade to STD ?
very kind
Shaun VermaakTechnical SpecialistCommented:
Shaun VermaakTechnical SpecialistCommented:
Question answered
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