CS 261 Final Exam p2

Which of the following circuit notations mean the same thing?

((a && b) || (c && d)) and (ab + cd) !(x && y) and (xy)'

What is the HCL/boolean expression for "a XOR b"?

(a && !b) || (!a && b)

Implementing a write to a register file requires

- A clock signal to trigger the action - A decoder to determine the register number The input data to the register

Implementing a read from a register files requires

- A clock signal to trigger the action - The output data from the register - A multiplexor to select the output of the register to read

All of the following are valid Y86 status codes:

- AOK - HLT - INS - ADR

What is true of combinational circuits?

- Circuits may not contain loops - Circuits may not contain gates - A gate may have more than two inputs - Gate inputs must be connected to a primary input, a memory output, or the output of another gate - The output of a gate may be connected to inputs for multiple gates.

What is true of a piplined system?

- Ideal pipelining requires uniform partitioning. - A pipelined system can increase throughput

Which of the following options are considered a characteristic of a RISC (Reducted Instruction Set Computer)?

- No instructions with a long execution time. - Fixed-length encodings - Implementations artifacts exposed to machine-level programs.

What is true about a memory hierarchy system?

- Storage devices get largers as we move form higher to lower levels - Storage devices get slower as we more from higher to lower levels - Storage devices get cheaper as we move from higher to lower levels

what are common types of device controllers that communicate with the CPU and main memory via the I/O bus

- USB controller - network controller - SATA controller - graphics card

All of the following are differences between Y86-64 and x84-64:

- Y86-64 has fewer data types - Y86-64 has only 3 condition codes - x86-64 uses %r15 as a general purpose register - x86-64 has the scaled index addressing mode

Which arithmetic instructions are included in Y86-64?

- addition - subtraction - bitwise AND

Assume that X = 5 and Y = 7. For the ALU what would be the output if the operation control signal is set to 0?

12

What is the little endian hex encoding of the following Y86-64 ssembly instruction "rrmovq %rdi, 0x1234(%rbp)"?

40754321000000000000

Which component for digital system computes functions on bits?

Combinational logic

What technology is used for flash memory?

EEPROM

A register file with two read ports and one write port has

Five inputs and two outputs

When does a clocked register's value change?

It depends on how the circuit is designed.

Which is the following is trye the the HCL/boolean expression (a && b) || (!a && !b)?

It is true if and only if a == b

What happens during the memory stage of a rmmovq instruction?

Memory is written at the location specified by the effective address

What happens during the decode stage of a jmp instruction?

Nothing.

What input values should never be used for an S-R latch?

S and R set to 1 at the same time.

what is true about how DRAM and SRAM use technologies to store infromation?

SRAM relies on transistors and DRAM relies on capacitors

S-R latches and D flip flops both store a bit. What kind of input is required by a D flip-flop that is not required in a S-R latch?

The D flip-flop requires a clock input.

What happens when the R bit is set to 1 (and the S bit is set to 0) in an S-R latch

The output is set to 0

What happens when the S bit is set to 1 (and the R bit is set to 0) in an S-R latch

The output is set to one

The minimum time that the input to a memory device must be valid before the clock edge is called

The set up time.

What happens during the execute and write back stages of a pushq instruction?

The stack pointer is decremented

Which of the following instructions does NOT require an eight-byte immediate value or destination address?

andq

A disk's capacity is most closely dependent upon

areal density

Which of the following Y86-64 instructions decrements the stack pointer?

call

Which of the following Y86-64 instructions does NOT modify the stack?

cmovle

Which two stages of execution read from or write to the register file?

decode and write back

During which stage of execution for jle instruction does the CPU detemine whether of not the branch should be taken?

execute

What is the central characteristic of the internal design of sequential circuits?

feedback

Which state of the execution does the CPU determine that an irmovq will use %rsi?

fetch

Which of the following instructions will set the processor status code to something other than AOK?

halt

The time required in a computing system to execute a single instruction is called the

latency

In Y86-64, which instruction moves a value from a memory location into a register?

mrmovq

Which combinational circuit component is used to select between one of several possible inputs?

multiplexor

disk controller maintains associtations betwee logical blocks and

physical sectors

Suppose a Y86-64 machine code instruction is two bytes long and its hex encoding is 20 45. What is the corresponding assembly code?

rrmovq %rsp %rbp

time it takes for a disk arm to position itself over the correct track to read data is called

seek time

cache memory is

small, fast buffer for larger, slower memory

The frequency is the inverse of

the clock cycle time

The minimum time during which the input must be valid after the clock edge is called

the hold time

IN a D flip-flop, "D" corresponds to

the input to the flip-flop

The number of instructions that can be executed per unit of time in a computer system is called the

throughput

For ret instruction, which internal field of the Y86 processor is used to update the PC?

valM

What is the output value of the circuit (x((x' + 1) + (yy')))?

x