The most I've seen a mobo support is 16GB at 2000MHz. Might be a bit behind, as I would expect X58 to raise that limit a bit to work better with tri-channel configs (as 16 does not go into 3 evenly; 18GB would make much more sense...)
It will depend on the kind of computer and the work you wanna do on it and not to forget the cost of it too, i have seen a Computer with the capability to support 192GB (DDR3 RDIMM Memory, 1066MHz, ECC 12 DIMMS at $198,080), yep a monster, this computer is use for Advanced engineering; 3D industrial design; digital content creation; demanding technical and scientific computing; complex multi-threaded/multitasking application environments. Dell work station , Hp Z 800 work station I'm not too sure about mac but the Mac pro go up to 32 GB hope that was helpful
Message edited by t-blan on 08-17-2009 at 05:49:57 AM