48-bit computing
In computer architecture, 48-bit integers can represent 281,474,976,710,656 discrete values. This allows an unsigned binary integer range of 0 through 281,474,976,710,655 or a signed two's complement range of −140,737,488,355,328 through 140,737,488,355,327. A 48-bit memory address can directly address every byte of 256 terabytes of storage. 48-bit can refer to any other data unit that consumes 48 bits in width. Examples include 48-bit Central [processing unit|CPU] and ALU architectures that are based on registers, address buses, or data buses of that size.
Word size
Computers with 48-bit words include the AN/FSQ-32, CDC 1604/upper-3000 series, BESM-6, Ferranti Atlas, Philco TRANSAC S-2000 and Burroughs large systems.The Honeywell DATAmatic 1000,
H-800,
the MANIAC II,
the MANIAC III,
the Brookhaven National Laboratory Merlin,
the Philco CXPQ,
the Ferranti Orion,
the Telefunken Rechner TR 440,
the ICT 1301,
and many other early transistor-based and vacuum tube computers
used 48-bit words.
Addressing
The IBM System/38, and the IBM AS/400 in its CISC variants, use 48-bit byte addresses. The minimal implementation of the x86-64 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 in logical block addressing was increased to 48 bits with the introduction of ATA-6. The Ext4 file system physically limits the file block count to 48 bits.
The media access control address of a network interface controller uses a 48-bit address space.