TCS Papers: Sample Questions 234 - 235 of 502

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Question number: 234

» Basic CS » Networks

Essay Question▾

Describe in Detail

What are the different link types used to build a computer network?

Explanation

  1. Cables

    These connect nodes in the same room, building, or even the same site (e. g. campus) using a piece of cable that physically strings between the nodes.

  2. Leased Lines

    Connects two nodes across large distances- on opposite sides of the country, or even across continents.

  3. Last-Mile Links

    “Last-mile” links are less expensive than leased lines- only span the last mile from network service provider.

  4. Wireless Links

    For example the mobile phone system.

Question number: 235

» Basic CS » Operating System

Essay Question▾

Describe in Detail

What is cycle stealing?

Explanation

  • We encounter cycle stealing in the context of Direct Memory Access (DMA).

  • Either the DMA controller can use the data bus when the CPU does not need it, or it may force the CPU to temporarily suspend operation- this is technique is called cycle stealing.

  • That cycle stealing can be done only at specific break points in an instruction cycle.

  • Cycle stealing is a method of accessing computer memory (RAM) or bus without interfering with the CPU.

  • It is similar to direct memory access (DMA) for allowing I/O controllers to read or write RAM without CPU intervention.

  • Clever exploitation of specific CPU or bus timings can permit the CPU to run at full speed without any delay if external devices access memory not actively participating in the CPU’s current activity and complete the operations before any possible CPU conflict.

  • Requests by DMA devices for using the bus are always given higher priority than processor requests.

  • Among different DMA devices, top priority is given to high-speed peripherals.

  • Since the processor originates most memory access cycles, it is often stated that DMA steals memory cycles from the processor.

  • If DMA controller is given exclusive access to the main memory to transfer a block of data without interruption, this is called block or burst mode.

Image of The Cycle steal mode

Image of the Cycle Steal Mode

Given the image is defining the cycle steal mode