Bissoy.com
Doctors Medicines MCQs Q&A

Consider the following code sequence having five instructions I1 to I5. Each of these instructions has the following format. OP Ri, Rj, Rk Where operation OP is performed on contents of registers Rj and Rk and the result is stored in register Ri I1: ADD R1, R2, R3 I2: MUL R7, R1, R3 I3: SUB R4, R1, R5 I4: ADD R3, R2, R4 I5: MUL R7, R8, R9 Consider the following three statements. S1: There is an anti-dependence between instructions I2 and I5 S2: There is an anti-dependence between instructions I2 and I4 S3: Within an instruction pipeline an anti-dependence always creates one or more stalls Which one of the above statements is/are correct?

Consider the following code sequence having five instructions I1 to I5. Each of these instructions has the following format. OP Ri, Rj, Rk Where operation OP is performed on contents of registers Rj and Rk and the result is stored in register Ri I1: ADD R1, R2, R3 I2: MUL R7, R1, R3 I3: SUB R4, R1, R5 I4: ADD R3, R2, R4 I5: MUL R7, R8, R9 Consider the following three statements. S1: There is an anti-dependence between instructions I2 and I5 S2: There is an anti-dependence between instructions I2 and I4 S3: Within an instruction pipeline an anti-dependence always creates one or more stalls Which one of the above statements is/are correct? Correct Answer Only S2 is true

Concept:

Anti- dependence: It is also known as write after read, occurs when an instruction requires a value that is later updates.

Anti-dependency can be overcome in pipeline using register renaming.

Explanation:

Instructions are:

I1: R1 = R2 + R3

I2: R7 = R1 * R3

I3: R4 = R1 – R5

I4: R3 = R2 + R4

I5: R7 = R8 * R9

Here, in this anti- dependencies (WAR) are:

I1 – I2

I1 – I3

I3 – I4

I4 – I1

I4 – I2

Statement 1: There is an anti-dependence between instructions I2 and I5

This statement is false, I2 and I5 don’t form any write after read operation. There is no anti dependency in this.

Statement 2: There is an anti-dependence between instructions I2 and I4

This statement is true, here I2 reads R3 and I4 writes it.

Statement 3: Within an instruction pipeline an anti-dependence always creates one or more stalls

This statement is false as anti- dependency can be removed by using register renaming in pipeline.

Related Questions

The rate expression for a heterogenous catalytic reaction is given by, - rA = K.KA PA(1 + KA.PA + Kr.PR), where K is surface reaction rate constant and KA and KR are absorption equilibrium constants of A and R respectively. If KR PR >> (1 + KA PA), the apparent activation energy EA is equal to (given E is the activation energy for the reaction and ΔHR and ΔHA are the activation energies of adsorption of R and A)
A 5-stage pipelined processor has Instruction Fetch (IF), Instruction Decode (ID), Operand Fetch (OF), Perform Operation (PO) and Write Operand (WO) stages. The IF, ID, OF and WO stages take 1 clock cycle each for any instruction. The PO stage takes 1 clock cycle for ADD and SUB instructions, 3 clock cycles for MUL instruction, and 6 clock cycles for DIV instruction respectively. Operand forwarding is used in the pipeline. What is the number of clock cycles needed to execute the following sequence of instructions? Instruction Meaning of instruction I0 : MUL R2, R0, R1 R2← R0 * R1 I1 : DIV R5, R3, R4 R5 ← R3 / R4 I2 : ADD R2, R5, R2 R2 ← R5 + R2 I3 : SUB R5, R2, R6 R5 ← R2 – R6
V1, V2, V3 and V4 are the volumes of four cubes of side lengths x cm, 2x cm, 3x cm and 4 cm respectively. Some statements regarding these volumes are given below :
(i) V1 + V2 + 2V3 4
(ii) V1 + 4V2 + V3 4
(iii) 2(V1 + V3) + V2 = V4
Which of these statements area correct ?
Letx(t) be the input and y(t) be the output of a continuous time system. Match the system properties P1, P2 and P3 with system relations R1, R2, P3, P4.
Properties
P1 : Linear but NOT time-invariant
P2 : Time-invariant but NOT linear
P3 : Linear and time-invariant
Relations
R1 : y(t) = t2x(t)
R2 : y(t) = t |x(t)|
R3 : y(t) = |x(t)|
R4 : y(t) = x(t - 5)
Pick out the wrong statement below:
I. For the same conversion, the holding time required in a batch reactor, is always equal to the space time required in a PFR.
II. Two mixed reactors of unequal size are available for producing a specified product, formed by a homogenous second order reaction. To achieve maximum production rate, the smaller reactor should be placed in series before the larger reactor.
III. Arrehenius equation describing the effect of temperature on rate constant is given by, $${\text{K}} = {\text{A}}.{{\text{e}}^{ - \frac{{{\text{Ea}}}}{{{\text{RT}}}}}}$$
IV. The mechanism for the decomposition of CH3CHO into CH4 and CO in presence of I2 is:
CH3CHO + I2 → CH3I + HI + CO; slow
CH3I + HI → CH4 + I2; fast
Then the rate of disappearance CH3CHO is equal to K.CCH3l.CHl and acts as a catalyst.
Given,
3H2 + CO = CH4 + H2O, KP = 101.84 and 4H2 + CO2 = CH4 + 2H2O, KP = 101.17
the KP for the reaction CO + H2O = CO2 + H2 is
Consider the following system of equations in three real variables x1, x2 and x3
2x1 - x2 + 3x3 = 1
3x1 - 2x2 + 5x3 = 2
-x1 - 4x2 + x3 = 3
This system of equations has
Let X1, X2 be two independent normal random variables with means μ1, μ2 and standard deviations σ1, σ2 respectively. Consider Y = X1 - X2; μ1 = μ2 = 1, σ1 = 1, σ2 = 2, Then,
The registers QD, QC, QB and QA shown in the figure are initially in the state 1010 respectively. An input sequence SI = 0101 is applied. After two clock pulses, the state of the shift registers (in the same sequence QD QC QB QA) is
Electronics mcq question image
Let $$\overrightarrow {\bf{L}} $$ = (Lx, Ly, Lz) denotes the orbital angular momentum operators of a particle and let L+ = Lx + i Ly and L- = Lx - i Ly. The particle is in aneigen state of L2 and Lz eigen values $${\hbar ^2}\left( {l + 1} \right)$$   and $$\hbar l$$  respectively. The expectation value of L+L- in this state is