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| Computer architecture bit widths |
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Incomputer architecture,48-bitintegers can represent 281,474,976,710,656 (248 or 2.814749767×1014) discrete values. This allows anunsigned binary integer range of 0 through 281,474,976,710,655 (248 − 1) or asignedtwo's complement range of −140,737,488,355,328 (−247) through 140,737,488,355,327 (247 − 1). A 48-bitmemory address can directly address every byte of 256terabytes of storage. 48-bit can refer to any otherdata unit that consumes 48bits (6octets) in width. Examples include 48-bitCPU andALUarchitectures that are based onregisters,address buses, ordata buses of that size.
Computers with 48-bitwords include theAN/FSQ-32,CDC 1604/upper-3000 series,BESM-6,FerrantiAtlas,PhilcoTRANSAC S-2000 andBurroughs large systems.[a][b]
The HoneywellDATAmatic 1000,H-800,theMANIAC II,theMANIAC III,theBrookhaven National Laboratory Merlin,[1]thePhilco CXPQ,theFerranti Orion,theTelefunken Rechner TR 440,theICT 1301,and many other early transistor-based and vacuum tube computers[2]used 48-bit words.
TheIBM System/38, and theIBM AS/400 in itsCISC variants, use 48-bit byte addresses. The minimal implementation of thex86-64 architecture provides 48-bit byte addressing encoded into 64 bits; future versions of the architecture can expand this without breaking properly written applications.
The address size used inlogical block addressing was increased to 48 bits with the introduction ofATA-6. TheExt4 file system physically limits the file block count to 48 bits.
The media access control address (MAC address) of anetwork interface controller uses a 48-bit address space.
In digital images, 48 bits per pixel, or 16 bits per each color channel (red, green and blue), is used for accurate processing. For the human eye, it is almost impossible to see any difference between such an image and a 24-bit image,[citation needed] but the existence of more shades of each of the three primary colors (65,536 as opposed to 256) means that more operations can be performed on the image without risk of noticeablebanding orposterization.