Published at LXer:

64-bit computing is as prevalent today as multicore computing. Almost any new processor from Intel or AMD has the AMD long mode extensions, allowing the processor to use 64-bit registers. While 32-bit processors can address 4 gigabytes of RAM, a 64-bit processor can address 16 exabytes, or almost 17.2 billion gigabytes, of RAM. Most 64-bit-capable computers aren't making use of these capabilities, but instead are put to work running 32-bit operating systems, usually because of a lack of applications for 64-bit operating systems, since applications must be recompiled and in some cases rewritten for 64-bit operation. It is possible, however, to run 32-bit Linux binaries natively under 64-bit Linux kernels.

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