Joseph CPS387/577 E. Lang Test #2 April 30, 2007 NAME_____________________________________________
This test is closed notes and closed book. You may not use scratch paper or a calculator on this test. 1. (10 points) The immediate mode instruction, LDI, loads the accumulator with the value stored in the instruction. The code for this instruction is 6XXX16, where the XXX is the immediate value to be loaded into the accumulator. For example, if the instruction is 612316, the value 12316 would be loaded into the accumulator. Give the full set of micro operations as specified by RTL for this instruction. The circuit diagram for our simple CPU is on Page 2 of this test.
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2. (15 points) Given the circuit diagram for our simple CPU (on Page 2 of this test), which of the following pairs of RTL actions can take place simultaneously (circle Y) and which can not (circle N)? Note: if either one of the RTL actions is impossible, circle N.
Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y
N N N N N N N N N N N N N N N
AR <- M[AR], PC <- PC + 1 IR <- M[AR], PC <- PC + 1 DR <- M[AR], IR <- 0 AC <- M[AR], PC <- PC + 1 AC <- DR, TR <- AR DR <- AC, TR <- DR AR <- AC +DR, PC <- PC + 1 AC <- AC + DR, M[AR] <- PC DR <- AC + DR, M[AR] <- PC M[AR] <- AC, DR <- 0 M[AR] <- DR, AC <- 0 M[AR] <- AC, DR <- DR + 1 M[AR] <- TR, IR <- IR + 1 M[AR] <- IR, TR <- 0 M[AR] <- AR, TR <- TR + 1
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3. a) (10 points) Suppose we wish to replace the ADD instruction of simple our CPU with the ADM instruction. The ADM instruction adds the contents of the accumulator to the memory location specified without changing the value stored in the accumulator. The indirect addressing version of this instruction holds the address of the address of the memory location to which the accumulator is added. The opcode for this instruction is 9XXX16. Write the RTL for the full set of micro operations for the fetch, decode and execute parts of this instruction. The circuit diagram for our simple CPU is on Page 2 of this test.
3. b) (10 points) If the accumulator initially contains the value 0001 and the ADM instruction is located at address 100, show the effect of this instruction by writing down the memory contents after execution of this instruction given the memory contents before execution as shown below. Address Memory Contents Before 100 9200 ... 200 0300 ... 300 0400 ... 400 0500 Memory Contents After
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4. (15 points) Name the different types of control units and give the advantages and disadvantages of each.
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(10 points) Can a computer with Harvard Architecture be SISD? Circle one -> YES NO. For full credit, explain.
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6. (15 points) List the ways that the problems of the Von Neumann bottleneck can be reduced. For each such way that you list, tell whether it would or would not require changes to the software running on the computer system.
7. (15 points) What changes (if any) would be required when a non-pipelined CPU is replaced by pipelined form of the same CPU.
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