Taking the RISC Out of CISC

　　已經有一個模糊的定義之間的RISC（精簡指令集計算機）和CISC（復雜指令集計算）架構的地步，在許多情況下，條款幾乎是毫無意義的。許多現代的RISC處理器比CISC處理器更復雜。事實上，它已不再是RISC和CISC指令定義之間的差異的數量，而是他們的表現方式的內存訪問。

　　盡管RISC風格建筑的例子可以在1960和1970年代發現，RISC的真正的歷史可以追溯到上世紀80年代。它背后的想法是，有一個更簡單的指令集，意味著這些指令可以更快地執行架構如果沒有指示，很少，如果以往的負擔，執行。

　　兩種最初的RISC體系結構分別是MIPS和Power體系結構，分別在斯坦福大學和加州大學伯克利分校開發。關鍵的一點是RISC系統使用了負載存儲結構。這里的內存通常是通過特定的指令訪問的，而不是作為其他指令的一部分訪問的。今天，當RISC系統已經變得比CISC架構越來越復雜，內存訪問系統看作是一個決定性的因素在RISC和CISC之間的區別。在最初的架構，早期的例子是休利特帕卡德PA-RISC和Sun公司的SPARC處理器。

　　CISC products， on the other hand， are typified by the x86 architectures， mainly from Intel but also from others such as AMD. Intel’s Pentium range is one of the best examples of CISC chips， Motorola’s 68000 series is another. However， CISC chips， despite the name， do not always use a complex architecture and these days many are less complex than RISC chips. Basically anything that does not use the load-store memory access system is often classed as CISC， whatever the architecture looks like. There is no doubt that a floating-point RISC architecture is much more complex than， say， an 8-bit CISC processor. Even the addressing modes on RISC chips are often more complex than with many CISC processors. Good examples of modern RISC processors are Microchip’s PIC? range and the devices from many manufactures that are based on ARM? cores.