In recent years, one of the more popular topics for panel discussions at computer conferences and trade (61) has been the "RISC versus CISC" debate.
RISC processors feature a small number of instructions that each executes in (62) machine cycle. CISC processors use complex instructions that can take several cycles to execute.
The RISC versus CISC debate won’t be decided by panel discussion; it will be won in the marketplace. And the deciding factor may have little to do with (63) of instructions and registers and more to do with parallelism.
Since their conception, RISC processors have been evolving toward micro parallelism, incorporating parallel-processing features (64) the processor, RISC processors feature pipelining, whereby many instructions can be decoded while one instruction executes. RISC processors, however, are moving toward pipelines for each unit of the processor.
CISC processors also employ pipelining. They have many integer instructions that execute in one cycle, but the varying execution times of CISC instructions (65) the effectiveness of parallelism.
A．union
B．two
C．numbers
D．between
E．limit
F．contents
G．shows
H．one
I．within
J．enhance
参考答案：E
解析：
[分析]： 近年来，“RISC VS CISC”的争论，是计算机会议和商业展览上最流行的专题讨论课题之一。
RISC处理器的特征是较小的指令集，每条指令在一个机器周期中执行。CISC处理器使用复杂指令集，每条指令可能花费若干个周期来执行。
其实，我们不必进行RISC和CISC之间的争议，让市场决定它们的胜负。并且决定因素也许很少取决于指令和寄存器的数目，而更多取决于并行性。
自从RISC概念提出后，RISC处理器正向着微并行性方向发展。它在处理器中简化了并行处理的特性。RISC处理器的特征为流水线，当一条指令在流水线上执行时，许多指令可以被解码。况且，RISC处理器正向着每个处理器单元有多条流水线方向发展。
CISC处理器也使用流水线。它们有许多一个周期执行时间的整数指令，但是CISC内部不同的执行时间的指令，限制了并行效率。