Big Picture: Classic 5 Components of A Processor

-- Control Unit  (in the processor)

-- Datapath      (in the processor)

-- Memory

-- Input

-- Output

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 HARDWARE DESIGN STEPS

1. analyze instruction set => datapath requirements

 

    ISA model => RTL model: the meaning of each instruction is given by the register transfers

    datapath must include storage element of ISA registers and possibly more

    datapath must support each register transfer

2. select set of datapath componets and build clocking methodology

3. assemble datapath meeting the RTL requirements

4. analyze implementation of each instruction to determine setting of ctrl points that effect the register transfer

5. assemble the ctrl logic

6. RTL datapath and ctrl design are refined

    timing and bug-fixing

    optimization for cost/performance (computering engineering is all about trade-off)

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 SELECT A SUBSET OF INSTRUCTIONS

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LOOK AT WHAT HAPPENS ON EACH INSTRUCTION

• 取出指令
• 解码并执行

MORE DETAILED DECOMPOSITION

• 取指 PC specifies a instruction and it get fetched from memory
• 解码 figure out every field of the instruction; read 1 or 2 regs as operands
• 执行 ALU does the math
• 访存 read a data for a LOAD; write a data for a STORE
• 回写 store results to memory or registers

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5 steps done in a clock cycle

purely combinational logic in that rectangle

this is what single-cycle computer means