42 Questions
What is the primary issue with the accumulator architecture?
It has an intrinsic performance problem.
Which of the following logic gates is used to implement binary multiplication with 'shift left' and additions?
AND
What is the purpose of the 1-bit multiplexer circuit shown in Fig. 2.5?
To select between two input signals.
How many instructions are required to implement the expression 'X' in the accumulator architecture?
19
What is the primary advantage of the RISC architecture over the CISC architecture?
RISC has a smaller instruction set.
What is the purpose of the 4-bit adder circuit shown in Fig. 2.4?
To perform addition operations.
Which phase of the instruction cycle is responsible for executing the instruction?
Effective instruction execution.
What is the expression implemented by the pseudo-code in Listing 2.7?
(C - D) × (A + B) - (E × F)
What is the primary function of the accumulator in the processor architecture depicted in Figure 2.3?
Arithmetic and logical operations
What type of instruction set architecture is implied by the microprogram in Figure 2.3?
RISC (Reduced Instruction Set Computing)
What is the purpose of the IR register in the microprogram?
Stores the opcode for the current instruction
What is the function of the logic gate in the binary arithmetic circuit?
Performs logical operations on binary numbers
What is the purpose of the DR register in the microprogram?
Stores the data fetched from memory
What is the effect of the instruction #16 Jump if positive on the program counter?
The program counter is set to the address specified in the instruction
What is the primary function of the Accumulator (ACC) in the given microprogram?
To perform arithmetic operations
What is the main difference between RISC and CISC architectures?
RISC uses a fixed instruction length, while CISC uses a variable instruction length
What is the primary purpose of the Address Register (AR) in the given microprogram?
To manage memory addresses
What is the function of the logic gate in the binary arithmetic circuit?
To make decisions based on input conditions
What is the purpose of the case 15 instruction in the microprogram?
To jump to a specified address
What is the role of the Data Register (DR) in the microprogram?
To hold the data temporarily
What is the function of the case 21 instruction in the microprogram?
To halt the processor
What is the purpose of the binary arithmetic circuit?
To perform arithmetic operations
In the accumulator-based architecture, what is the primary function of the ACC register?
To perform arithmetic operations and hold the result
In the load-store architecture, what is the purpose of the data register (DR)?
To store the data temporarily during load and store operations
What is the purpose of the instruction register (IR) in the microprogram?
To decode the instruction opcode
In the microprogram representation, what is the purpose of the switch statement?
To dispatch the correct micro-operation based on the opcode
What is the addressing mode used in the instruction 'LOAD'?
Register indirect addressing
What is the effect of the instruction 'JUMP IF POSITIVE' on the program counter?
The program counter is set to the address field value only if the accumulator is positive
What is the primary advantage of using a microprogram representation?
It makes it easier to design and implement complex instruction sets
In the accumulator-based architecture, which register holds the memory address during the execution of an instruction?
Address Register (AR)
What is the role of the address register (AR) in the microprogram?
To hold the address field value of the instruction
What is the primary advantage of the load-store architecture over the accumulator-based architecture?
More efficient use of memory
In the microprogram representation, what is the function of the Instruction Register (IR)?
Decodes the opcode
Which addressing mode is implied by the microprogram in Figure 2.3?
Direct addressing
What is the purpose of the Data Register (DR) in the microprogram?
Stores the data operands
Which of the following is a characteristic of the accumulator-based architecture?
Uses a single accumulator register for all operations
In the accumulator-based architecture, which register is responsible for storing the address of the memory location to be accessed?
Address Register (AR)
What is the primary difference between the accumulator-based architecture and the load-store architecture?
The way data is accessed and stored
What is the purpose of the Instruction Register (IR) in the microprogram?
To store the instruction being executed
What type of addressing mode is used in the microprogram representation shown in Fig. 2.3?
Indirect addressing
What is the function of the Data Register (DR) in the accumulator-based architecture?
To store the data being processed
What is the role of the Program Counter (PC) in the microprogram?
To keep track of the current instruction being executed
Study Notes
Processor Operation and Instructions
- The given pseudo-code in Listing 2.7 is equivalent to the expression:
(C − D) × (A + B) − (E × F) / (H − I) × (F + G) - The expression can be implemented using a 4-bit adder circuit, 1-bit multiplexer, and binary multiplication with "shift left" and additions.
Logic Gates
- Basic logic gates used to implement circuits include:
- AND gate
- NOT gate
- NAND gate
- Truth tables are provided for these gates in Figures 2.6 to 2.8.
Phases of Processor Operation
- The processor operation consists of five phases:
- Operation code fetch
- Operation code decode
- Operands fetch
- Effective instruction execution
- Results store
Accumulator Architecture
- The accumulator architecture has an intrinsic performance problem.
- The accumulator code version implementing the expression "X" is shown in Listing 2.8.
- The code has 19 instructions.
Microprogram
- The microprogram related to the processor with accumulator architecture is shown in Figure 2.3.
- The microprogram behaves as follows:
- Verify the operation code to execute
- Execute the corresponding operation (LOAD, STORE, ADDITION, JUMP, JUMP IF POSITIVE, STOP)
Microprogram Pseudo-Code
- The microprogram pseudo-code is shown in Listing 2.5 and 2.6.
- The code includes instructions for:
- LOAD operation
- STORE operation
- ADDITION operation
- JUMP operation
- JUMP IF POSITIVE operation
- STOP operation
Microprogram Pseudo-Code
- The microprogram pseudo-code has a switch statement that verifies the operation code to execute based on the instruction register (IR).
- There are several cases in the switch statement, each corresponding to a specific operation:
LOAD Operation
- Case 1: AR (address register) gets the address field from DR (data register).
- DR gets the contents of memory at the address indexed by AR.
- ACC (accumulator register) gets the value from DR.
STORE Operation
- Case 2: AR gets the address field from DR.
- DR gets the accumulator value.
- Memory position indexed by AR gets the value from DR.
ADDITION Operation
- Case 5: AR gets the address field from DR.
- DR gets the contents of memory at the address indexed by AR.
- ACC gets the sum of the accumulator value and DR value.
JUMP Operation
- Case 15: PC (program counter) gets the address field value from DR.
JUMP IF POSITIVE Operation
- Case 16: If the accumulator value is greater than zero, PC gets the address field value from DR.
STOP Operation
- Case 21: The processor halts.
Microprogram Pseudo-Code Example (Listing 2.7)
- The example consists of several operations:
STORE Operation
- AR gets the PC value.
- AR gets the address field from DR.
- DR gets the accumulator value.
- Memory position indexed by AR gets the value from DR.
ADDITION Operation
- IR gets the opcode from DR.
- AR gets the address field from DR.
- DR gets the contents of memory at the address indexed by AR.
- ACC gets the sum of the accumulator value and DR value.
JUMP Operation
- PC gets the address field value from DR.
JUMP IF POSITIVE Operation
- If the accumulator value is greater than zero, PC gets the address field value from DR.
STOP Operation
- The processor halts.
Microprogram and Processor Architecture
- The microprogram represents the processor with accumulator architecture.
- The processor consists of:
- Data Register (DR)
- Address Register (AR)
- Program Counter (PC)
- Instruction Register (IR)
- Arithmetic Logic Unit (ALU)
- Memory
- Control Unit
Simplify the given pseudo-code to evaluate the expression X. The code involves operations on variables A, B, C, D, E, F, G, H, and I. Evaluate the expression X and simplify it.
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