What is the maximum memory that Windows 8 64-bit and Windows 8.1 64-bit support in their base editions?

A maximum of 128GB of memory is supported by Windows 8 and 8.1 64-bit. Other Windows 8 versions provide up to 512GB of storage. This is a Microsoft limitation, not a limitation in 64-bit operating systems. A 64-bit operating system will theoretically support up to 16 Exabytes of memory!