Computer Desktop Encyclopedia
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128-bit
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bit specifications
Everything in the digital world is measured in bits and bytes. Bits are a measurement of different components and functions depending on what is being referenced. Following are the most common. See binary values.
CPU
The size of the computer's internal registers. This is the computer's "word" size, which is the amount of data the CPU can compute at the same time. Theoretically, if the clock rates were the same (800 MHz, 1 GHz, 2 GHz, etc.) and the basic architectures were equal, a 32-bit computer would work twice as fast internally as a 16-bit computer. In practice, 8-bit, 16-bit, 32-bit and 64-bit architectures are rarely identical to each other even from the same manufacturer. Thus, a 64-bit computer may be (internally) less than twice as fast or more than twice as fast as a 32-bit computer.
In order to take advantage of a CPU with larger words, operating systems and applications must be recompiled with a compiler that supports the larger word size. If not, the older software may actually run slower in the bigger CPU, but this is totally dependent on the mix of instructions used in the program.
Most important, this measurement does not result in twice as much actual work being done for the user, as the computer's cache size and bus and disk speeds are all part of the performance equation.
System Bus
The size of the computer's system bus (frontside bus), which is the pathway over which data are transferred between memory and the CPU and between memory and the peripheral devices. If the bus clock rates are equal, a 32-bit bus transfers data twice as fast as a 16-bit bus.
Address Bus
The size of the address bus, which determines how much memory the CPU can address directly. Each bit doubles the number, for example, 20 bits addresses 1 megabyte (MB); 24 bits addresses 16 megabytes (MB); 32 bits addresses 4 gigabytes (GB). See binary values.
Color Depth
The number of colors that can be displayed at one time. This is called "bit depth," "color depth" and "pixel depth." Unless some of the memory is used for cursor or sprite movement, an 8-bit display adapter generates 256 colors; 16-bit, 64K colors; 24-bit, 16.8 million colors. See alpha channel and bit depth.
Bit specifications, such as 64-bit and 128-bit, refer to the display adapter's architecture, which affects speed, not the number of colors. See 64-bit graphics accelerator and 128-bit graphics accelerator.
Sound Sample
The quality of sound based on the number of bits in the samples taken. A 16-bit sample yields a number with 65,536 increments compared to 256 in an 8-bit sample. See 8-bit sample and 16-bit sample.
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128-bit
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128-bit
| Processors | |||||||||||||
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| 1-bit | 4-bit | 8-bit | 12-bit | 16-bit | 18-bit | 24-bit | 31-bit | 32-bit | 36-bit | 48-bit | 60-bit | 64-bit | 128-bit |
| Applications | |||||||||||||
| 8-bit | 16-bit | 32-bit | 64-bit | ||||||||||
| Data sizes | |||||||||||||
| bit nibble octet byte | |||||||||||||
| halfword word dword qword | |||||||||||||
| IEEE floating-point standard | |||||||||||||
| Single precision floating-point format (32-bit) Double precision floating-point format (64-bit) Quadruple precision floating-point format (128-bit) | |||||||||||||
In computer architecture, 128-bit integers, memory addresses, or other data units are those that are at most 128 bits (16 octets) wide. Also, 128-bit CPU and ALU architectures are those that are based on registers, address buses, or data buses of that size. 128-bit is also a term given to a generation of computers in which 128-bit processors are the norm. There are currently no mainstream general-purpose processors built to operate on 128-bit integers or addresses, though a number of processors do operate on 128-bit data. The IBM System/370 could be considered the first rudimentary 128-bit computer as it used 128-bit floating point registers. Most modern CPUs feature SIMD instruction sets (SSE, AltiVec etc.) where 128-bit vector registers are used to store several smaller numbers, such as four 32-bit floating-point numbers, and a single instruction can operate on all these values in parallel. However, these processors do not operate on individual numbers that are 128 binary digits in length, only their registers have the size of 128-bits.
The DEC VAX supported operations on 128-bit integer ('O' or octaword) and 128-bit floating-point ('H-float' or HFLOAT) datatypes. Support for such operations was an upgrade option rather than being a standard feature. Since the VAX's registers were 32 bits wide, a 128-bit operation used four consecutive registers or four longwords in memory.
Uses
- 128 bits is a common key size for symmetric ciphers in cryptography. It is also the size of Globally Unique Identifiers and IPv6 addresses.
- 128-bit processors could be used for addressing directly up to 2128 (over 3.40 × 1038) bytes, which would greatly exceed the total data stored on Earth as of 2010, which has been estimated to be around 1.2 zettabytes (over 270 bytes).[1]
- Quadruple precision (128-bit) floating point numbers can store qword (64-bit) fixed point numbers or integers accurately without losing precision. Notice that since the Intel 8087 (1980), x86 architecture supports 80-bit floating points that store and process 64-bit signed integers (-263...263-1) accurately.
- The AS/400 virtual instruction set defines all pointers as 128-bit. This gets translated to the hardware's real instruction set as required, allowing the underlying hardware to change without needing to recompile the software. Past hardware was 32-bit CISC, while current hardware is 64-bit PowerPC. Because pointers are defined to be 128-bit, future hardware may be 128-bit without software incompatibility.
- Increasing the word size can speed up multiple precision mathematical libraries. Applications include cryptography.
History
A 128-bit multicomparator was described by researchers in 1976.[2]
A CPU with 128-bit multimedia extensions was designed by researchers in 1999.[3]
References
- ^ Rich Miller (May 2010). "Digital Universe nears a Zettabyte". The Guardian (datacenterknowledge.com). http://www.datacenterknowledge.com/archives/2010/05/04/digital-universe-nears-a-zettabyte/. Retrieved 16 September 2010.
- ^ Mead, C.A.; Pashley, R.D.; Britton, L.D.; Daimon, Y.T.; Sando, S.F. (1976). "128-bit multicomparator". IEEE Journal of Solid-State Circuits 11: 692. doi:10.1109/JSSC.1976.1050799. http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1050799.
- ^ Suzuoki, M.; Kutaragi, K.; Hiroi, T.; Magoshi, H.; Okamoto, S.; Oka, M.; Ohba, A.; Yamamoto, Y. et al (1999). "A microprocessor with a 128-bit CPU, ten floating-point MAC's, four floating-point dividers, and an MPEG-2 decoder". IEEE Journal of Solid-State Circuits 34: 1608. doi:10.1109/4.799870. http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=799870.
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