128-bit computing

In <a href="/facts/Computer_architecture/tHtwxgR2">computer architecture</a>, 128-bit <a href="/facts/Integer_(computer_science)/zWabo5M9">integers</a>, <a href="/facts/Memory_address/7EsUmbea">memory addresses</a>, or other <a href="/facts/Data_(computing)/cPjfFHph">data</a> units are those that are 128 <a href="/facts/Bit/RwfjaYSv">bits</a> (16 <a href="/facts/Octet_(computing)/dqCHsuUF">octets</a>) wide. Also, 128-bit <a href="/facts/Central_processing_unit/Jxp1bqMV">central processing unit</a> (CPU) and <a href="/facts/Arithmetic_logic_unit/SgIjPzSc">arithmetic logic unit</a> (ALU) architectures are those that are based on <a href="/facts/Processor_register/32RvbUdz">registers</a>, <a href="/facts/Address_bus/R45TKwS7">address buses</a>, or <a href="/facts/Bus_(computing)/R45TKwS7">data buses</a> of that size.
General home computing and gaming utility emerged at 8-bit word sizes, as 28=256 <a href="/facts/Word_(computer_architecture)/2e5umRaj">words</a>, a natural unit of data, became possible. Early 8-bit CPUs (such as the <a href="/facts/Zilog_Z80/Jeqe2h55">Zilog Z80</a> and <a href="/facts/MOS_Technology_6502/q9YLwkzm">MOS Technology 6502</a>, used in the 1977 <a href="/facts/Commodore_PET/08R12Xk4">PET</a>, <a href="/facts/TRS-80/zNfQKxnQ">TRS-80</a>, and <a href="/facts/Apple_II/se82CNvK">Apple II</a>) inaugurated the era of personal computing. Many 16-bit CPUs already existed in the mid-1970s. 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 = 18,446,744,073,709,551,616 unique words, 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 <a href="/facts/Names_of_large_numbers/J8c2407m">quintillion</a> (1.8×1019) to 340 <a href="/facts/Names_of_large_numbers/J8c2407m">undecillion</a> (3.4×1038) 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 <a href="/facts/History_of_general-purpose_CPUs/vz4m3lKL">general-purpose processors</a> 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 are given in § History.

128-bit computing open-in-new

128-bit computing