The limit is 4 gigabytes on a standard i386™ install. Beginning with FreeBSD versions 4.9 and 5.1, more memory can be supported through pae(4). This does require a kernel recompile, with an extra option to enable PAE:
options PAE
FreeBSD/pc98 has a limit of 4 GB memory, and PAE can not be used with it. On FreeBSD/alpha, the limit on memory depends on the type of hardware in use - consult the Alpha Hardware Release Notes for details. Other architectures supported by FreeBSD have much higher theoretical limits on maximum memory (many terabytes).
