128-bit computing

General home computing and gaming utility emerge at 8-bit (but not at 1-bit or 4-bit) word sizes, as 28=256 words become possible. Thus, early 8-bit CPUs (TRS 80, 6502, Intel 8088 introduced 1976-1981 by Commodore, Tandy Corporation, Apple and IBM) inaugurated the era of personal computing. Many 16-bit CPUs already existed in the mid-1970's. Over the next 30 years, the shift to 16-bit, 32-bit and 64-bit computing allowed, respectively, 216=65,536 unique words, 232=4,294,967,296 unique words and 264=18,446,744,073,709,551,615 unique words respectively, each step offering a meaningful advantage until 64 bits was reached. Further advantages evaporate from 64-bit to 128 bit computing as the number of possible values in a register increases from roughly 18 quintillion (1.8e19) to 340 undecillion (3.40e38) as so many unique values are never utilized. Thus, with a register that can store 2128 values, no advantages over 64-bit computing accrue to either home computing or gaming. CPUs with a larger word size also require more circuitry, are physically larger, require more power and generate more heat. Thus, there are currently no mainstream general-purpose processors built to operate on 128-bit integers or addresses, although a number of processors do have specialized ways to operate on 128-bit chunks of data, and uses are given below. A processor with 128-bit byte addressing could directly address up to 2128 (over 3.40e38) bytes, which would greatly exceed the total data captured, created, or replicated on Earth as of 2018, which has been estimated to be around 33 zettabytes (over 274 bytes). A 128-bit register can store 2128 (over 3.40 × 1038) different values. The range of integer values that can be stored in 128 bits depends on the integer representation used. With the two most common representations, the range is 0 through 340,282,366,920,938,463,463,374,607,431,768,211,455 (2128 − 1) for representation as an (unsigned) binary number, and −170,141,183,460,469,231,731,687,303,715,884,105,728 (−2127) through 170,141,183,460,469,231,731,687,303,715,884,105,727 (2127 − 1) for representation as two's complement.