Test: Machine Instructions & Addressing Modes - Computer Science Engineering (CSE) MCQ

C) Relative Mode since we can just change the content of base register if we wish to relocate.

(A) Base addressing - Position independent (By changing value in Base register location of address can be changed)

(B) Indexed addressing - Array

(C) Stack addressing - Reentranecy (Whenever code happens to be used again, address need not be the same)

(D) Implied addressing - Accumulator (If an address is not specified, it is assumed/implied to be the Accumulator)

In the case of, auto increment the increment is done afterward and in auto decrement the decrement is done first.

Answer: B
Relative mode addressing is most relevant to writing a position-independent code.

PC relative addressing mode:

The effective memory address is obtained by computing an offset from the current PC. No matter where the code is loaded in memory, the offsets are always the same so the code needs no modification. In this addressing, there is absolutely no change in code needed.

Therefore the answer is Option 4 i.e, PC relative Addressing

Pointers can not be implemented if the processor supports only immediate and direct addressing modes. Pointer requires indirect addressing modes.

C is the most appropriate one

(A) is the answer.
Array implementation can use Indexed addressing
While passing array as parameter we can make use of a pointer (as in C) and hence can use Indirect addressing
Base Register addressing can be used to write relocatable code by changing the content of Base Register.

(b) is the answer. Absolute addressing mode means address of operand is given in the instruction.
(a) operand is inside the instruction -> immediate addressing
(c) register containing the address in specified in operand-> register Indirect addressing
(d) the location of operand is implicit-> implicit addressing

Answer: C
A displacement type addressing should be preferred. So, I is not the answer.
Indirect Addressing leads to extra memory reference which is not preferable at run time. So, IV is not the answer.

1 memory read - get first operand from memory address A+R0 (A is given as part of instruction)
1 memory read - get address of second operand (since second uses indirect addressing)
1 memory read - to get second operand from the address given by the previous memory read
1 memory write - to store to first operand (which is the destination)
So, totally 4 memory cycles once the instruction is fetched.

(c) is the answer.
A[i] = B[j]; Indexed addressing
while(*A++); Auto increment
temp = *x; Indirect addressing

As relative addresses are calculated from absolute addresses, So relative addressing cannot be faster than absolute addressing.

D) Memory location 1001 has value 20.
R_s  1 (Immediate Addressing)

R_d  1 (Indexed Addressing, value at memory location 1+1000 = 1001 is loaded to R_d which is 1)
( R_d becomes 1+1000)
store in address  1001   20

In auto increment addressing mode, the base address is incremented after operand fetch. This is useful in fetching elements from an array. But this has no effect in self-relocating code (where code can be loaded to any address) as this
works on the basis of an initial base address.
An additional ALU is desirable for better execution especially with pipelining, but never a necessity.
Amount of increment depends on the size of the data item accessed as there is no need to fetch a part of a data.
So, answer must be C only.

Answer: D
Base Index Addressing, as the content of register R2 will serve as the index and 20 will be the Base address.

Option (D)

Displacement Mode :-
Similar to index mode, except instead of a index register a base register will be used. Base register contains a pointer to a memory location. An integer (constant) is also referred to as a displacement. The address of the operand is obtained by
adding the contents of the base register plus the constant. The difference between index mode and displacement mode is in the number of bits used to represent the constant. When the constant is represented a number of bits to access the
memory, then we have index mode. Index mode is more appropriate for array accessing; displacement mode is more appropriate for structure (records) accessing.

daisy chaining approach tell the processor i which order the interrupt should be handled by providing priority to the devices
In daisy chaining method all the devices are connected in serial. The device with the highest priority is placed in the first position, followed by lower priority devices . interrupt pin is common to all
so answer is a

2000 KB is transferred in 11 second

 44 KB transfer is (4/2000)∗1000 ms

= 2 ms

Total cycle required for locking and handling of interrupts after DMA transfer control

=(1000+500) clock cycle =1500 clock cycle

Now, 50 Mhz = 50∗10⁶ = 0.02 microsecond

So, (1500∗0.02)=30 microsecond

30μs for initialization and termination and  2ms for data transfer.

The CPU time is consumed only for initialization and termination.

Fraction of CPU time consumed =30μs/(30μs+2ms)

= 0.015

Explanation:

- DMA I/O (1) High speed RAM: DMA (Direct Memory Access) is used for transferring data between peripherals and memory without involving the CPU. It is commonly used for high-speed data transfers to and from high-speed RAM.

- Cache (2) Disk: Cache memory is a small, fast type of volatile computer memory used to temporarily store data that is frequently accessed. It helps in reducing the access time to data stored on slower storage devices like disks.

- Interrupt I/O (3) Printer: Interrupt I/O involves the use of interrupts to signal the CPU that a peripheral device needs attention. This is commonly used for devices like printers where the CPU needs to be informed when data is ready to be printed.

- Condition Code Register (4) ALU: The Condition Code Register (CCR) is a register used to store the condition codes generated by the ALU (Arithmetic Logic Unit) during arithmetic and logical operations. These codes are used to determine the outcome of operations and make decisions based on them.