Linux on PowerPC
Posted Jul 15, 2010 10:57 UTC (Thu) by Yorick
Parent article: Linux on PowerPC
This is because the 64-bit PowerPC processors have no "32-bit mode" like the Intel 64/AMD64 architecture. Hence, 64-bit PowerPC programs that do not need 64-bit mathematical functions will run somewhat slower than their 32-bit counterparts because 64-bit pointers and long integers consume twice as much memory, fill the CPU cache faster, and thus need more frequent memory accesses.
PowerPC processors do have 32 and 64 bit modes, but in contrast to x86, the 32-bit mode is not restricted to fewer or smaller registers, so the only benefit of running something in 64-bit mode is the larger address space. "64-bit mathematical functions" have nothing to do with it; a 32-bit process can use 64-bit operations and registers.
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