64-bit computing

64-bit computing

Refers to CPUs that process 64 bits as a single unit. Although CPUs migrated to 64-bits years ago, the vast majority of people still run 32-bit applications in their 64-bit personal computers. In 2003, AMD's Opteron and Athlon were the first 64-bit CPUs for PCs, and the G5 was the first 64-bit Mac CPU.

New versions of Windows come in 32-bit and 64-bit versions, and Apple's Snow Leopard upgraded all core OS components to 64 bits in 2009. The complete migration from 32-bit applications to their 64-bit counterparts will take many years, if ever. For example, users still run 16-bit Windows applications that were written more than two decades ago.

The 64-bit mode does not result in two times as much real work getting done as in a 32-bit computer, because it relates to internal processing. Disk, memory, cache and bus sizes and speeds play important roles in a computer's performance (see throughput). See 32-bit computing, Intel 64, G5 and bit specifications.

                  Bytes       Typical
      CPU       Processed     Memory
  Environment  At one time    Capacity

    64-bit        8           GB to TB

    32-bit        4           4GB +

    16-bit        2           1MB

     8-bit        1           65KB