CPUs that process 128 bits as a single unit, compared to 8, 16, 32 or 64 bits. As of 2022, there are no 128-bit computers on the market. A 128-bit processor may never occur because there is no practical reason for doubling the basic register size.
One of the reasons for migrating from 32-bit to 64-bit computers was memory (RAM) addressing; however, for all practical purposes, there was only a need for a few more bits beyond 32 (see binary values). Using all bits in a 64-bit register could theoretically manage 18 quintillion bytes of RAM.
128-Bits Do Exist for Other Purposes
The graphics and floating point circuits in today's 32-bit and 64-bit computers are 128 bits and more (see SSE). Computers also operate on multiple sets of data simultaneously that are stored in vector registers 128, 256 and 512 bits in length. In addition, 128 and 256 bits are commonly used for encryption keys (see secret key cryptography). See 128-bit graphics accelerator, 8-bit computing, 16-bit computing, 32-bit computing, 64-bit computing and bit specifications.
