Dictionary.net

A term describing a computer architecture basedaround an ALU, registers and data bus which are 64bits wide.64-bit processors were quite common in 1996, e.g. DigitalAlpha, versions of Sun SPARC, MIPS, IBM AS/4000.the PowerPC and Intel were expected to move to 64 bits attheir next generation - PPC 620 and Intel P7.A 64-bit address bus allows the processor to address 18million gigabytes as opposed to the mere 4 gigabytes allowedwith 32 bits. There were in 1996 already hard disks whichcan hold over 4GB. Floating point calculations can also bemore accurate.A 64-bit OS is needed as well to take advantage of the CPU.In 1996 there were only a few 64-bit operating systems,including OS/400, Digital Unix, Solaris (partialy). A32-bit OS can run on a 64-bit CPU.