[CentOS] Memory Not Recognized

> I noticed that my CentOS 6.5 system reports that I only have about 10.9
> GiB of RAM when I actually have 16384M. I have already tried adding
> mem=xxM to the end of the kernel line in grub.conf. The result is the
> same. Any suggestions?

Is this a Dell or other major server vendor system that happens to have 
memory sparing turned on in the BIOS?  I assume that other major server 
vendors do something like this as well where they save one dimm per bank 
in case of a dimm failure, the faulty one is switched out for the spare.

Barry