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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 ...
(In the examples that follow, a, b, and c are (direct or calculated) addresses referring to memory cells, while reg1 and so on refer to machine registers.) C = A+B 0-operand (zero-address machines), so called stack machines: All arithmetic operations take place using the top one or two positions on the stack: [9] push a, push b, add, pop c.
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 B5000 was the first stack machine and also the first computer with a segmented virtual memory. The Burroughs B5000 instruction set includes the set of valid operations for the B5000, B5500 and B5700. It is not compatible with the B6500, B7500, B8500 or their successors.
In a simple two-address format of instructions, [d] there is no way to change the address, so 1,000 additions have to be written in the machine language. ISAs fix this problem with the concept of indirect addressing, in which the address of the next point of data is not a constant, but itself held in memory or a machine register. This means the ...
Instruction cryptoleq a, b, c Mem[b] = O 1 (Mem[a], Mem[b]) if O 2 (Mem[b]) ≤ 0 IP = c else IP = IP + 3 where a, b and c are addressed by the instruction pointer, IP, with the value of IP addressing a, IP + 1 point to b and IP + 2 to c. In Cryptoleq operations O 1 and O 2 are defined as follows:
Decoding the op-code in the instruction register includes determining the instruction, determining where its operands are in memory, retrieving the operands from memory, allocating processor resources to execute the command (in super scalar processors), etc.
Single instruction, multiple data. Single instruction, multiple data (SIMD) is a type of parallel processing in Flynn's taxonomy.SIMD can be internal (part of the hardware design) and it can be directly accessible through an instruction set architecture (ISA), but it should not be confused with an ISA.