My mac has 4gb of memory but with nothing running it only has 3gb why Tags: Memory Macintosh Last response: February 10, 2012 9:48 PM in Memory Share mamama February 10, 2012 9:44:44 PM my mac should have 4 gb of memory but even with nothing running im only getting at most 3gb. any ideas? More about : mac 4gb memory running 3gb mikeangs2004 February 10, 2012 9:48:51 PM You have 32 bit OS which can not recognize more than 3-4Gb of RAM. The OS might have reserved 1Gb for internal system use. If your hardware supports 64-bit you can upgrade it... m 0 l Can't find your answer ? Ask ! Publish Related resources SolvedDo I need 4gb graphics memory if I'm only running two monitors? Forum MSI 865PE Neo2-PFISR BIOS reporting only 3GB of memory with 4GB instal Forum Why can a 32-bit os only recognize slightly over 3gb of memory Forum More resources Read discussions in other Memory categories Compatibility DDR2 DDR3 Dual Channel RAM Corsair G.SKILL !