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In a stack machine, the operands used in the instructions are always at a known offset (set in the stack pointer), from a fixed location (the bottom of the stack, which in a hardware design might always be at memory location zero), saving precious in-cache or in-CPU storage from being used to store quite so many memory addresses or index ...
A stack machine has most or all of its operands on an implicit stack. Special purpose instructions also often lack explicit operands; for example, CPUID in the x86 architecture writes values into four implicit destination registers.
Separate from the stack definition of a MISC architecture, is the MISC architecture being defined by the number of instructions supported. Typically a minimal instruction set computer is viewed as having 32 or fewer instructions, [1] [2] [3] where NOP, RESET, and CPUID type instructions are usually not counted by consensus due to their fundamental nature.
The Burroughs Large Systems Group produced a family of large 48-bit mainframes using stack machine instruction sets with dense syllables. [NB 1] The first machine in the family was the B5000 in 1961, which was optimized for compiling ALGOL 60 programs extremely well, using single-pass compilers.
The simple model provided in a stack-oriented language allows expressions and programs to be interpreted simply and theoretically evaluated much faster, since no syntax analysis needs to be done but lexical analysis. The way such programs are written facilitates being interpreted by machines, which is why PostScript suits printers well for its use.
Further improvements can be found by providing the address of both of the operands in a single instruction, for instance, ADD address 1, address 2. Such "two-address format" ISAs are very common. One can further extend the concept to a "three-address format" where the SAVE is also folded into an expanded ADD address 1, address 2, address of result.