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Showing posts from November, 2012

Orthogonal instruction set

Definition: "In computer engineering, an orthogonal instruction set is an instruction set architecture where  all instruction types  can use  all addressing modes . It is 'orthogonal' in the sense that the instruction type and the addressing mode vary independently." The story of orthogonal instruction set: In the past, because the  memory is very precious , so the processor designer tends to  make instructions as powerful as possible . So they hope one instruction can perform  full function  like get data from memory and then perform the calculation. They make  all instructions can have all the addressing modes . By this way,  one instruction can fetch data and do the calculation at the same time .  But this will  inscrease the complexity  of the processor design. Also, accessing memory directly is very time-consuming, so some companies choose to use RISC processor (like ARM) which has a  LOAD-STORE a...