[Solved] CPU ram limitations.

It basically boils down to how many memory ranks a certain CPU can support. Any dual-channel CPU that can't use registered memory can support four dual-ranked DIMMs. The exact quantity supported at any particular point in time depends on how large of memory ICs memory makers are putting on DIMMs at a given time. DDR3 is supposed to allow for 8 Gbit memory ICs, which means 8 GB per rank of 8 ICs, and 16 GB per dual-ranked module. Nobody makes 8 Gbit ICs yet- they only make 4 Gbit ones at best- so the maximum dual-ranked module size right now is 8 GB. So, both are correct- you can put no more than 32 GB (four 8 GB modules) in the system today, but in the future you can put up to 64 GB in there (four 16 GB modules.)

Dual-socket machines and servers play according to different rules because they can use registered memory. That allows for more memory modules per channel than systems like the E3-1245 that only use unbuffered memory. They can also have larger memory modules because registered memory allows for quad-rank DIMMs and also four-bit-wide memory ICs, so theoretically you can have up to 64 GB in a single registered DDR3 DIMM, whereas unbuffered tops out at 16 GB per DIMM. A dual Socket G34 Opteron setup can support 12 registered DIMMs per CPU and up to 64 GB per DIMM, giving a maximum capacity of 768 GB per socket. Currently they could have up to 384 GB per socket since 64 GB quad-ranked registered DIMMs don't exist yet, but 32 GB ones do.