# Recent questions and answers in CO and Architecture

1
A CPU has $24$-$bit$ instructions. A program starts at address $300$ (in decimal). Which one of the following is a legal program counter (all values in decimal)? $400$ $500$ $600$ $700$
2
A bit-map can be used to keep track of which blocks are free in a file-system’s partition on disk. Assuming, 1 KB block size and a disk size of 40 GB, what is the size of the bit map?
1 vote
3
A $3.5$ inch micro floppy high density disk contains the data _________ . $720 \: MB$ $1.44 \: MB$ $720 \: KB$ $1.44 \: KB$
4
Suppose there are 500 memory references in which 50 misses in the 1st level cache and 20 misses in the 2nd level cache . Let the miss penalty from L2 cache to memory is 100 cycles . Hit time in L2 cache is 20 cycles and hit time in L1 cache is 10 cycles ... number of stall cycles per instruction will be __________ Ans is : 15 Can any explain how to solve this type of question, Thanks in advance.
5
Consider the following processor design characteristics: Register-to-register arithmetic operations only Fixed-length instruction format Hardwired control unit Which of the characteristics above are used in the design of a RISC processor? I and II only II and III only I and III only I, II and III
6
The principle of locality justifies the use of: Interrupts DMA Polling Cache Memory
7
A hard disk with a transfer rate of 1 KBps is constantly transferring data to memory using DMA cycle stealing mode. The size of the data transfer is 16 bytes. The processor runs at 400 kHz clock frequency. The DMA controller requires 10 cycles for initialization ... and preparation time as 0.9375 sec and percentage time CPU gets blocked = transfer time/preparation time (IN case of cycle stealing)
8
CPU can leave current instruction execution, without completing it for : Service of interrupt DMA Both Neither
9
The storage area of a disk has the innermost diameter of $10$ cm and outermost diameter of $20$ cm. The maximum storage density of the disk is $1400$ bits/cm. The disk rotates at a speed of $4200$ RPM. The main memory of a computer has $64$-bit word length and $1$µs ... data transfer from the disk, the percentage of memory cycles stolen for transferring one word is $0.5 \%$ $1 \%$ $5\%$ $10\%$
10
Consider a disk drive with the following specifications: $16$ surfaces, $512$ tracks/surface, $512$ sectors/track, $1$ KB/sector, rotation speed $3000$ rpm. The disk is operated in cycle stealing mode whereby whenever one $4$ byte word is ready it is sent to memory; similarly, ... is $40$ nsec. The maximum percentage of time that the CPU gets blocked during DMA operation is: $10$ $25$ $40$ $50$
11
A direct mapped cache memory of $1$ MB has a block size of $256$ bytes. The cache has an access time of $3$ ns and a hit rate of $94 \%$. During a cache miss, it takes $2$0 ns to bring the first word of a block from the main memory, while each subsequent word takes $5$ ns. The word size is $64$ bits. The average memory access time in ns (round off to $1$ decimal place) is______.
12
Consider a two level memory hierarchy, L1 (cache) has an accessing time of 5 ns and main memory has an accessing time of 100 ns. Writing or updating contents takes 20 ns and 200 ns for L1 and main memory respectively. Assume L1 gives misses 20% of the time with 60% of the instructions are read only instructions. What is the average access time for system (in ns) if it uses WRITETHROUGH technique?
13
Consider the following program fragment in the assembly language of a certain hypothetical processor. The processor has three general purpose registers $R1, R2$and $R3$. The meanings of the instructions are shown by comments (starting with ;) after the instructions. X: CMP R1, 0; ... $R3$ when control reaches $Z$?
14
Can we apply LRU policy to direct mapped cache. according to me it doesn't make any sense as eventually it will be like FIFO only as unique memory addresses are assigned to each cache line. But my doubt / confusion is can we implement LRU on direct mapped caches?
15
An access sequence of cache block addresses is of length $N$ and contains n unique block addresses. The number of unique block addresses between two consecutive accesses to the same block address is bounded above by $k$. What is the miss ratio if the access sequence is passed through a cache of ... $\left(\dfrac{1}{N}\right)$ $\left(\dfrac{1}{A}\right)$ $\left(\dfrac{k}{n}\right)$
1 vote
16
A hypothetical processor on cache read miss requires one clock to send an address to Main Memory (MM) and eight clock cycles to access a 64-bit word from MM to processor cache. Miss rate of read is decreased from 14.8% to 2.6% when line size of cache is ... four words. The speed up of processor is achieved in dealing with average read miss after increasing the line size is (Upto 2 decimal places)
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18
A hypothetical 5 stage pipeline processor is designed in which branch is predicted at 3rd stage and each stage takes 1 cycle to compute its task. If p is a the probability of an instruction being a branch instruction then the value of p such that speed up is atleast 3 is ________. (Upto 2 decimal places)
1 vote
19
Consider a non­pipelined processor design which has a cycle time of 10ns and average CPI of 1.4. The maximum speedup pipelined processor can get by pipelining it into 5 stages and each stage takes 2ns is
20
if a instruction pipeline has 5 stages with different stage delays 2 , 3 , 4 , 5, 6 ns . The pipeline registers are required between each stage and at the end of last stage. each register delay is 1ns. How the time taken by a NON-PIPELINED implementation is calculated for n no. of instructions? and what is the speed up here?
21
here why to take stall at the highlighted cell as its OPERAND FORWARDING and unless mentioned its EX-EX and its being followed without stall also, please clarify how to understand where Operand Forwarding is to be applied in such generalized cases., Thanks in advance :)
22
Data forwarding is used to avoid which type of conflict?? (1) RAW (2) WAR (3) WAW (4) RAR
23
Which of the following is true? S1: If there is a cycle in RAG then there will be a deadlock S2: If there is a cycle in RAG where all the resources are havinng single instance then there will be a deadlock S3: Unsafe state results in deadlock S4: Deadlock states is subset of unsafe states (A) S4 only (B) S2 & S4 only (C) S1 & S4 only (D) S1, S3 & S4 only
24
Comparing the time $T1$ taken for a single instruction on a pipelined CPU, with time $T2$ taken on a non-pipelined but identical CPU, we can say that ______ ? $T1=T2$ $T1>T2$ $T1<T2$ $T1$ is $T2$ plus time taken for one instruction fetch cycle.
25
A pipeline is having speed up factor as $10$ and operating with efficiency of $80\%.$ What will be the number of stages in the pipeline? $10$ $8$ $13$ None
26
Micro program is: the name of a source program in micro computers set of microinstructions that defines the individual operations in response to a machine-language instruction a primitive form of macros used in assembly language programming a very small segment of machine code
27
is the CPI of RISC processor always 1?
28
A micro program control unit is required to generate a total of 25 control signals. Assume that during any micro instruction, at most two control signals are active. The number of bits required in the control word to generate the required control signals ... In this question I am asking about horizontal microprogramming) previous year gate question link:https://gateoverflow.in/2754/gate1996-2-25
29
A micro programmed control unit Is faster than a hardwired unit Facilitates easy implementation of a new instruction Is useful when small programs are to be run All of the above
30
Suppose the functions F and G can be computed in 8 and 3 nanoseconds by functional units UF and UG, respectively. Given three instances of UF and three instances of UG, it is required to implement the computation F(G(Xi)) for 1 ≤ i ≤ 13. A control Unit selects next task/s and ... complete this computation is ( in nanoseconds): (A) 28 (B) 33 (C) 43 (D) 49 my answer is 43 but gatebook answer is 49.
1 vote
31
Which of the following is an efficient method of cache updating? Snoopy writes Write through Write within Buffered write
32
In a cache memory if total number of sets are ‘$s$’, then the set offset is: $2^8$ $\log_2s$ $s^2$ $s$
33
A computer has 32 bit instruction and 12 bit address . If there are 250 two address instructions , the no. of one -address instructions can be ..... Plz formulate a generic solution for this with diagram .
34
Match each of the high level language statements given on the left hand side with the most natural addressing mode from those listed on the right hand side.$\begin{array}{clcl} \text{(1)} &\text{$A[I] = B[J]$} & \qquad\text{(a)} &\text{Indirect addressing} \\ \text{(2)} &\text{while$ ... $(1, c), (2, c), (3, b)$ $(1, b), (2, c), (3, a)$ $(1, a), (2, b), (3, c)$
35
The Data transfer instruction size is $64-bit$ ALU, ALU operation instruction size is $32-bit$ and branch instruction size is $16-bit$. Assume program has been loaded in the memory starting from address 3000 decimal. If an interrupt occurs during the execution of $I-6$, ... When $I-6$ is executing, PC value will be 3030, but given answer is 3028 Previous Q: https://gateoverflow.in/1058/gate2004-63
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INCA(Increase register A by $1$) is an example of which of the following addressing mode? Immediate addressing Indirect addressing Implied addressing Relative addressing