X4140 server not able to detect 32 GB Memory

All,

We have installed 16 x 2 GB memory DIMMS in Sun Fire X4140 server. I have verified from systems ilom, it is able to detect all 16 DIMMS of 2 GB and there is no fault on system ilom. System is able to properly boot-up. During POST process, it only able to detect 20 GB RAM.
Below details of SP version and OS details..

SP version details:
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SP Firmware Version  3.0.6.16 
SP Firmware Build Number  50656 
SP Firmware Date  Thu Dec 3 20:05:30 PST 2009 
SP Filesystem Version  0.1.22 
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OS/Patch level and File systems:
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-bash-3.2# cat /etc/release
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