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All questions of Memory Hierarchy: Cache, Main Memory and Secondary Storage for Computer Science Engineering (CSE) Exam

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The small extremly fast, RAM’s all called as ________
  • a)
    Cache
  • b)
    Heaps
  • c)
    Accumulators
  • d)
    Stacks
Correct answer is option 'B'. Can you explain this answer?

Maitri Yadav answered
Answer: b
Explanation: Cache’s are extremly essential in single BUS organisation to achieve fast operation.

The read/write heads must be near to disk surfaces for better storage. 
  • a)
    True
  • b)
    False
Correct answer is option 'A'. Can you explain this answer?

Mahi Yadav answered
Answer: a
Explanation: By maintaining the heads near to the surface greater bit densities can be achieved.

 The last on the hierarchy scale of memory devices is ______
  • a)
    Main memory
  • b)
    Secondary memory
  • c)
    TLB
  • d)
    Flash drives
Correct answer is option 'B'. Can you explain this answer?

Dipika Chavan answered
Hierarchy Scale of Memory Devices

There are different types of memory devices used in computer systems. These memory devices are arranged in a hierarchy based on their speed, capacity, and cost. The hierarchy scale of memory devices is as follows:

1. Registers
2. Cache memory
3. Main memory
4. Secondary memory
5. Tertiary memory

Explanation

Secondary memory is the last on the hierarchy scale of memory devices. This is because secondary memory is slower and cheaper than other memory devices. Secondary memory is used to store data and programs that are not currently being used by the CPU. Examples of secondary memory devices include hard disk drives, solid-state drives, and magnetic tape.

Secondary memory devices have a higher storage capacity than main memory devices, which makes them suitable for storing large files and data that are not frequently accessed. However, the access time of secondary memory devices is slower than that of main memory devices, which makes them less suitable for storing data that needs to be accessed quickly.

Conclusion

In conclusion, secondary memory is the last on the hierarchy scale of memory devices. It is slower and cheaper than other memory devices, but it has a higher storage capacity. Secondary memory devices are used to store data and programs that are not currently being used by the CPU. Examples of secondary memory devices include hard disk drives, solid-state drives, and magnetic tape.

The reason for the fast operating speeds of the flash drives is
  • a)
    The absence of any movable parts
  • b)
    The itegarated electronic hardware
  • c)
    The improved bandwidth connection
  • d)
    All of the mentioned
Correct answer is option 'A'. Can you explain this answer?

Mahi Yadav answered
Reasons for the fast operating speeds of flash drives:

1. Absence of movable parts:
Flash drives use solid-state technology, which means they do not have any moving parts like traditional hard drives. This absence of moving parts allows flash drives to operate at faster speeds because there is no mechanical latency in accessing data. The lack of moving parts also reduces the risk of physical damage or failure, making flash drives more reliable and durable.

2. Integrated electronic hardware:
Flash drives contain integrated electronic hardware that allows for quick data transfer and access. The integrated circuitry within a flash drive enables it to communicate with the computer or device it is connected to efficiently. This hardware design contributes to the overall speed of the flash drive and allows for fast read and write operations.

3. Improved bandwidth connection:
Flash drives are designed to take advantage of high-speed interfaces such as USB 3.0, USB 3.1, or Thunderbolt. These interfaces provide increased bandwidth for data transfer, resulting in faster operating speeds for flash drives. The improved connection speed allows for quicker file transfers, making flash drives a convenient and efficient storage solution.

4. Conclusion:
The combination of the absence of movable parts, integrated electronic hardware, and improved bandwidth connection all contribute to the fast operating speeds of flash drives. These factors make flash drives a popular choice for portable storage due to their speed, reliability, and durability.

A control bit called ____ has to be provided to each blocj in set-associative.
  • a)
    Idol bit
  • b)
    Valid bit
  • c)
    Reference bit
  • d)
    All of the mentioned
Correct answer is option 'B'. Can you explain this answer?

Gitanjali Singh answered
Control Bit in Set-Associative Cache

Introduction:
In computer architecture, a cache is a small but fast memory that stores frequently accessed data and instructions for faster retrieval. Set-associative cache is a type of cache organization that combines the benefits of direct-mapped and fully-associative caches. It divides the cache into multiple sets, and each set contains multiple cache blocks.

Control Bits:
Control bits are additional bits associated with each cache block that provide important information about the block's status and usage. One such control bit in set-associative cache is the Valid Bit.

Valid Bit:
The valid bit is used to indicate whether a particular cache block in a set-associative cache is valid or not. It is a single control bit that is associated with each cache block.

- When the valid bit is set to 1, it means that the corresponding cache block contains valid data.
- When the valid bit is set to 0, it means that the corresponding cache block does not contain valid data and should not be used for cache operations.

Importance of Valid Bit:
The valid bit is crucial in set-associative cache because it helps in efficient cache management and prevents unnecessary cache accesses. Here are a few reasons why the valid bit is important:

1. Cache Initialization: During the initialization of the cache, all valid bits are typically set to 0. This indicates that the cache blocks are empty and do not contain valid data. As data is fetched into the cache from the main memory, the valid bits are set to 1 to indicate that the blocks now contain valid data.

2. Cache Lookup: When a processor requests data from memory, the cache controller needs to search for the data in the cache. The valid bits help in this search process by allowing the cache controller to quickly identify the cache blocks that contain valid data. It avoids unnecessary searches in empty or invalid cache blocks.

3. Cache Replacement: In set-associative cache, when a cache block needs to be replaced with a new block, the valid bit of the replaced block is set to 0, indicating that it no longer contains valid data. This allows the cache controller to reuse the block for storing new data.

4. Cache Coherency: Valid bits are also used in cache coherency protocols to maintain consistency between multiple caches in a system. When a cache block is modified, the valid bit is typically set to 0 to indicate that the data in other caches may be stale and needs to be updated.

Therefore, the valid bit is an essential control bit in set-associative cache that helps in cache management, efficient lookup, replacement, and cache coherency.

The DMA doesn’t make use of the MMU for bulk data transfers. 
  • a)
    True
  • b)
    False
Correct answer is option 'B'. Can you explain this answer?

Deepika Chauhan answered
The DMA stands for the Direct Marketing Association. It is a trade association that represents the direct marketing industry. The DMA provides resources, education, and advocacy for companies and professionals involved in direct marketing.

Direct marketing refers to marketing efforts that involve directly contacting individuals or businesses to promote products or services. This can include methods such as direct mail, email marketing, telemarketing, and more. The DMA works to promote ethical and responsible practices within the direct marketing industry.

The DMA offers various benefits to its members, including access to research, industry events, networking opportunities, and educational resources. The association also provides guidelines and best practices for direct marketers to follow, ensuring that they adhere to privacy regulations and maintain high standards of professionalism.

In addition to supporting its members, the DMA also advocates for the direct marketing industry as a whole. It works to influence legislation and regulations that impact direct marketing, and promotes the value and effectiveness of direct marketing as a marketing channel.

Overall, the DMA plays a crucial role in supporting and promoting the direct marketing industry and its professionals.

 In order to read multiple bytes of a row at the same time, we make use of ______
  • a)
    Latch
  • b)
    Shift register
  • c)
    Cache
  • d)
    Memory extension
Correct answer is option 'A'. Can you explain this answer?

Pritam Goyal answered
Answer: a
Explanation: The latch makes it easy to ready multiple bytes of data of the same row simulteneously by just giving the consecutive column address.

The data is transfered over the RAMBUS as _______
  • a)
    Packets
  • b)
    Blocks
  • c)
    Swing voltages
  • d)
    Bits
Correct answer is option 'C'. Can you explain this answer?

Maulik Iyer answered
Answer: c
Explanation: By using voltage swings to transfer data, transfer rate along with efficiency is improved.

The special communication used in RAMBUS are _________
  • a)
    RAMBUS channel
  • b)
    D-link
  • c)
    Dial-up
  • d)
    None of the mentioned
Correct answer is option 'A'. Can you explain this answer?

Vandana Desai answered
RAMBUS is a special high-speed communication technology used in computer systems. It is known for its fast data transfer rates and efficient performance. Below are some key points explaining the special communication used in RAMBUS:
- RAMBUS Channel:
The special communication used in RAMBUS is known as the RAMBUS channel. This channel is designed to provide high-speed data transfer between the memory and the processor in a computer system.
- High Speed:
One of the main features of the RAMBUS channel is its high-speed data transfer capabilities. It allows for faster communication between the memory and processor, resulting in improved system performance.
- Efficient Performance:
The RAMBUS channel is designed to be efficient in terms of data transfer and processing. It optimizes the communication between components in the system, reducing latency and improving overall performance.
- Advanced Technology:
RAMBUS technology is considered advanced and innovative in the field of computer systems. It has been widely used in various applications where high-speed communication is required.
In conclusion, the special communication used in RAMBUS is the RAMBUS channel, which offers high-speed data transfer, efficient performance, and advanced technology in computer systems.

The set associative map technique is a combination of the direct and associative technique. 
  • a)
    True
  • b)
    False
Correct answer is option 'A'. Can you explain this answer?

Shounak Yadav answered
Answer: a
Explanation: The combination of the efficiency of the associative method and the cheapness of the direct mapping, we get the set-associative mapping.

Which of the following is an efficient method of cache updating?
  • a)
    Snoopy writes
  • b)
    Write through
  • c)
    Write within
  • d)
    Buffered write
Correct answer is option 'A'. Can you explain this answer?

Raksha Mishra answered


Explanation:

Snoopy writes:
- Snoopy write is an efficient method of cache updating where the cache controller monitors or snoops the bus for write requests to main memory.
- When a write request is detected, the cache controller updates the corresponding cache line to ensure data consistency between the cache and main memory.
- This method helps in keeping the cache coherent without the need for the processor to intervene in the write process.

Write through:
- Write through is a caching strategy where data is written to both the cache and main memory simultaneously.
- While this ensures data consistency, it may lead to performance overhead due to the additional write operations to main memory for every write request.

Write back:
- Write back is a caching strategy where data is only written to the cache initially, and the main memory is updated when the cache line is replaced.
- This strategy can be more efficient in terms of performance compared to write through, as it reduces the number of writes to main memory.

Buffered write:
- Buffered write is a technique where write operations are first stored in a buffer before being written to main memory.
- This can improve performance by allowing multiple write requests to be batched together and sent to main memory in a single operation.
- However, this method may introduce additional complexity and potential risks related to data consistency.

In conclusion, Snoopy writes is considered an efficient method of cache updating as it helps in maintaining cache coherence without significant performance overhead.

When two or more clock cycles are used to complete data transfer it is called as ________
  • a)
    Single phase clocking
  • b)
    Multi-phase clocking
  • c)
    Edge triggered clocking
  • d)
    None of the mentioned
Correct answer is option 'B'. Can you explain this answer?

Devika Kaur answered
Multi-phase clocking

Multi-phase clocking refers to a clocking scheme in digital systems where two or more clock cycles are used to complete data transfer. It provides a way to increase the efficiency and performance of data transfer operations by dividing them into multiple phases or steps.

Advantages of multi-phase clocking:
1. Improved performance: By dividing the data transfer process into multiple phases, each phase can be executed in a shorter amount of time. This allows for faster data transfer rates and improved system performance.

2. Reduced power consumption: Multi-phase clocking can help reduce power consumption as each phase operates at a lower frequency compared to a single-phase clocking scheme. This can be beneficial for battery-powered devices or systems with strict power constraints.

3. Enhanced timing control: With multi-phase clocking, each phase can be precisely controlled, allowing for better synchronization and timing accuracy. This is particularly important in high-speed systems where timing violations can lead to data corruption or other errors.

4. Increased scalability: Multi-phase clocking provides a scalable solution for data transfer. As the system requirements and data transfer rates increase, additional phases can be easily added to accommodate the higher data throughput.

Example:
One common implementation of multi-phase clocking is the use of a double data rate (DDR) interface in memory systems. In DDR memory, data is transferred on both the rising and falling edges of the clock signal, effectively doubling the data transfer rate compared to a single data rate (SDR) interface. This is achieved by dividing the data transfer process into two phases: read and write.

During the read phase, data is sampled on the rising edge of the clock, while during the write phase, data is captured on the falling edge of the clock. By utilizing both edges of the clock, DDR memory can achieve higher data transfer rates without increasing the clock frequency.

Conclusion:
Multi-phase clocking is a technique used in digital systems to improve performance, reduce power consumption, enhance timing control, and increase scalability. By dividing the data transfer process into multiple phases, the efficiency and overall system performance can be significantly improved.

The memory transfers between two variable speed devices is always done at the speed of the faster device. 
  • a)
    True
  • b)
    False
Correct answer is option 'A'. Can you explain this answer?

Atharva Kulkarni answered
Explanation:

When two devices with different speeds communicate and transfer data, the transfer speed is limited to the speed of the slower device. However, when it comes to memory transfers, the scenario is different. The memory transfer speed between two variable speed devices is always done at the speed of the faster device. The reason behind this is that the memory transfer speed is not affected by the clock speed of the devices.

The speed of the memory transfer is determined by the memory controller, which is responsible for managing the data transfer between the CPU and the memory. The memory controller is designed to operate at a specific speed, which is usually faster than the clock speed of the CPU. Therefore, when two devices with different speeds communicate with each other, the memory controller sets the transfer speed to match the speed of the faster device.

For example, if a CPU with a clock speed of 2 GHz is communicating with a memory device with a speed of 1 GHz, the memory transfer speed will still be 2 GHz, which is the speed of the CPU. This is because the memory controller is designed to operate at a speed of 2 GHz, which is faster than the speed of the memory device.

Conclusion:

In conclusion, the memory transfer speed between two variable speed devices is always done at the speed of the faster device. This is because the memory controller is responsible for managing the data transfer, and it operates at a specific speed that is usually faster than the clock speed of the CPU. Therefore, the transfer speed is not affected by the speed of the slower device.

__________ is the bootleneck, when it comes computer performance.
  • a)
    Memory access time
  • b)
    Memory cycle time
  • c)
    Delay
  • d)
    Latency
Correct answer is option 'B'. Can you explain this answer?

Rajveer Chatterjee answered
Memory cycle time

Memory cycle time can be considered as the time taken by the memory to complete one cycle, which includes both the time taken to access the memory and the time taken to transfer the data. It is an important factor that affects the overall performance of a computer system.

Understanding the bottleneck

A bottleneck refers to a point in a system where the flow of data is limited or constrained, causing a slowdown in overall performance. In the context of computer performance, a bottleneck can occur in various components such as the CPU, memory, storage, or network. In this case, the bottleneck is related to memory performance.

The impact of memory cycle time on computer performance

Memory cycle time plays a crucial role in determining the overall speed and efficiency of a computer system. When the memory cycle time is high, it means that the memory is taking longer to complete each cycle, resulting in slower data access and transfer. This can significantly impact the overall performance of the system.

Memory access time vs. memory cycle time

Memory access time refers to the time taken by the memory to locate and retrieve data. It is a subset of the memory cycle time. On the other hand, memory cycle time includes both the time taken for memory access and the time taken for data transfer.

Why memory cycle time is the bottleneck

Memory cycle time is considered the bottleneck when it comes to computer performance because it directly affects the overall speed and efficiency of data processing. When the memory cycle time is high, it slows down the entire system as the CPU has to wait longer for data to be fetched from memory or written back to memory. This can result in increased latency and delays in executing instructions, ultimately impacting the overall performance of the system.

Conclusion

In conclusion, memory cycle time is the bottleneck when it comes to computer performance. It directly affects the speed and efficiency of data processing, causing delays and increased latency. Therefore, optimizing memory cycle time is crucial for improving the overall performance of a computer system.

In a three BUS architecture, how many input and output ports are there ?
  • a)
    2 output and 2 input
  • b)
    1 output and 2 input
  • c)
    2 output and 1 input
  • d)
    1 output and 1 input
Correct answer is option 'C'. Can you explain this answer?

Aditya Nair answered
Three BUS Architecture

In a three BUS architecture, there are multiple buses that connect different components of a computer system. Each bus is responsible for transferring data between specific sets of components. In this architecture, there are two types of buses: input bus and output bus.

Input and Output Ports

- Input ports: These ports are used to receive data from external devices or other components of the computer system. They allow the computer to accept input from sources such as keyboards, mice, and other devices. The data received through the input ports is then processed by the computer.

- Output ports: These ports are used to send data from the computer system to external devices or other components. They allow the computer to provide output to devices such as monitors, printers, and speakers. The data sent through the output ports is displayed or used by the connected devices.

Understanding the Options

a) 2 output and 2 input: This option implies that there are two output ports and two input ports. However, in a three BUS architecture, there are typically more than two ports of each type to accommodate the connection of multiple devices.

b) 1 output and 2 input: This option implies that there is one output port and two input ports. Again, this contradicts the typical configuration of a three BUS architecture, where there are more than one output and input ports.

c) 2 output and 1 input: This option correctly states that there are two output ports and one input port. In a three BUS architecture, this configuration allows for multiple devices to receive data from the computer system while only one device can send data to the computer.

d) 1 output and 1 input: This option implies that there is only one output port and one input port. However, in a three BUS architecture, multiple devices need to be connected to both the input and output buses to facilitate communication.

Conclusion

In a three BUS architecture, the correct configuration for input and output ports is option 'C': 2 output and 1 input. This configuration allows for multiple devices to receive data from the computer system while only one device can send data to the computer.

The Zin signal to the processor is generated using, Zin = T1+T6 ADD + T4 .BR… 
  • a)
    True
  • b)
    False
Correct answer is option 'A'. Can you explain this answer?

Nishanth Mehta answered
Explanation:

Calculation of Zin signal:
- The Zin signal to the processor is generated using the formula: Zin = T1 + T6 ADD + T4
- This formula combines different terms T1, T6 ADD, and T4 to produce the Zin signal.

Interpretation of the formula:
- T1 represents one component of the Zin signal.
- T6 ADD represents another component of the Zin signal, which is added to T1.
- T4 represents an additional component that influences the Zin signal.

Conclusion:
- Therefore, the statement provided in the question is true. The Zin signal to the processor is indeed generated using the given formula: Zin = T1 + T6 ADD + T4.

The RAMBUS requires specially designed memory chips similar to _____
  • a)
    SRAM
  • b)
    SDRAM
  • c)
    DRAM
  • d)
    DDRRAM
Correct answer is option 'C'. Can you explain this answer?

Ishaan Saini answered
Answer: c
Explanation: The special memory chip should be able to transmit data on both the edges and is called as RDRAM’s.

Chapter doubts & questions for Memory Hierarchy: Cache, Main Memory and Secondary Storage - 6 Months Preparation for GATE CSE 2025 is part of Computer Science Engineering (CSE) exam preparation. The chapters have been prepared according to the Computer Science Engineering (CSE) exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for Computer Science Engineering (CSE) 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.

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