Previous Exams: Previous exams are available through the individual web pages. This final may be significantly different from previous ones. In particular, last semester I covered topics from caches (Chapter) and from buses (Section 8.4), but I did not cover these topics this semester, so there will be no final exam questions on these topics.

Review topics: Here are the new topics since the second exam, mainly just Chapter 6 on the pipelined implementation. Note that the final will emphasize Chapter 6, since.)

• Exceptions and the trap handler in MIPS (Lab 10).
  • The specifics of how the trap handler works.
  • Take-home quiz on exceptions: quiz

• Pipelined Implementation (Chapter 6)
  • Overview (Section 6.1, includes especially discussion of hazards).
  • Pipelined datapath (Section 6.2, ignores hazards). Note the several ways of graphically representing pipelines on pages 461-465, especially the series of diagrams in Figures 6.22-6.24.
  • Pipelined control (Section 6.3, ignores hazards). The control signals from the Control unit are the same as for the single-cycle implementation, but the pipelined implementation makes use of extra latched register storage between pipeline stages to pass along control information. (See Figures 6.29 and 6.30. See also the good series of diagrams in Figures 6.31-6.35.)
  • Data hazards and forwarding (Section 6.4). You should understand how forwarding works, with the Forwarding Unit and extra control and data lines. This applies to dependencies between the register result of one instruction and the use of that new register value in subsequent instructions. (See especially Figure 6.38 and the series of diagrams in Figures 6.41-6.42. We did not cover Figure 6.43 or page 488.)
  • Data hazards and stalls (Section 6.5). In case of a dependency involving a lw instruction, the machine must stall for one instruction. This uses the Hazard Detection Unit. Note how the stall is inserted by de-asserting write lines to the PC and the IF/ID registers, and by inserting all zeros on control lines. (These zeros propagate along from cycle to cycle, as the "bubble" of a stalled instruction moves along the pipeline.) See diagrams in Figures 6.47-6.49. Note that the final forwarding is done by the Forwarding Unit as before.
  • Branch hazard (Section 6.6). In case of a branch, if the branch is taken (in one simple implementation), must stall and wipe out the start of the next instruction. (Also need to move branch handling into step 2 of pipeline.) See Figures 6.51 and 6.52. Skip Section 6.6 from pape 501 on.
  • Exceptions (Section 6.7). Example of arithmetic overflow. IF.Flush, ID.Flush, EX.Flush lines to put nop in first stage and to set control lines to zeros in second and third stages.

• No questions about the use of CMOS transistors to create gates.
• Probably several questions about MIPS assembly and machine language. I might ask for the code for a simple loop (use of beq or bne), or for a simple call to a function (jal) and the code for the function (jr $ra to return), or access to memory (use of lw or sw).
• Possibly one question about the correspondence between machine code and assembler code (as in Lab 8: Hand Assembly of MIPS Code.
• At least one question on either the single-cycle or multi-cycle implementation. This might even ask you to do something creative, such a implementing a new instruction. The text has exercises asking how to implement the addi instruction in both the single-cycle and the multi-cycle models, without additional control lines. (Instruction decode does have to recognize the new instruction.)
• Extra emphasis on the pipelining chapter, the first seven sections.
  • I might ask about the pipelined datapath or pipelined control (lots of figures in sections 6.2, 6.3).
  • I plan to give you a diagram with a forwarding unit, for you to explain how the forwarding unit works in simple cases not involving a stall (section 6.4, figures 6.41, 6.42).
  • I might ask about the hazard detection unit and stall used to handle the lw instruction (section 6.5, figures 6.47, 6.48, 6.49).
  • I might ask about handling the beq instruction by moving everything into step 2, and by putting in a 1-cycle stall bubble (for successful branch) (section 6.6, figures 6.51, 6.52).
  • I might ask about handling arithmetic overflow exception by flushing the pipeline and restarting the instruction at address 40000040 (section 6.7, figures 6.55, 6.56).
• Probably one question about exception handlers.
• Perhaps one question about coding theory, probably the Hamming code.

Good Luck!!!