Which characteristics of RISC systems could be directly implemented in CISC systems? Which characteristics of RISC machines could not be implemented in CISC machines (based on the defining characteristics of both architectures as listed in Table 8.1)?

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TABLE 8.1 The Characteristics of RISC Machines Versus CISC Machines RISC Multiple register sets, often consisting of more than 256 registers Three register operands allowed per instruction (e.g., add R1, R2, R3) Parameter passing through efficient on-chip register windows Single-cycle instructions (except for load and store) Hardwired control Highly pipelined Simple instructions that are few in number Fixed-length instructions Complexity in compiler Only load and store instructions can access memory CISC Single register set, typically 6 to 16 registers total One or two register operands allowed per instruction (e.g., add R1, R2) Parameter passing through inefficient off-chip memory Multiple-cycle instructions Microprogrammed control. Less pipelined Many complex instructions Variable-length instructions Complexity in microcode Many instructions can access memory