ISRO-2018
February 13, 2024Question 22 – ISRO-2018
February 13, 2024ISRO-2018
| Question 16 |
Of the following, which best characterizes computers that use memory-mapped I/O?
| The computer provides special instructions for manipulating I/O ports | |
| I/O ports are placed at addresses on the bus and are accessed just like other memory locations | |
| To perform I/O operations, it is sufficient to place the data in an address register and call channel to perform the operation | |
| I/O can be performed only when memory management hardware is turned on |
Question 16 Explanation:
→ Memory-mapped I/O uses the same address space to address both memory and I/O devices.
→ The memory and registers of the I/O devices are mapped to (associated with) address values.
→ So when an address is accessed by the CPU, it may refer to a portion of physical RAM, or it can instead refer to the memory of the I/O device. Thus, the CPU instructions used to access the memory can also be used for accessing devices.
→ Each I/O device monitors the CPU’s address bus and responds to any CPU access of an address assigned to that device, connecting the data bus to the desired device’s hardware register.
→ To accommodate the I/O devices, areas of the addresses used by the CPU must be reserved for I/O and must not be available for normal physical memory.
→ The reservation may be permanent, or temporary (as achieved via bank switching).
→ The memory and registers of the I/O devices are mapped to (associated with) address values.
→ So when an address is accessed by the CPU, it may refer to a portion of physical RAM, or it can instead refer to the memory of the I/O device. Thus, the CPU instructions used to access the memory can also be used for accessing devices.
→ Each I/O device monitors the CPU’s address bus and responds to any CPU access of an address assigned to that device, connecting the data bus to the desired device’s hardware register.
→ To accommodate the I/O devices, areas of the addresses used by the CPU must be reserved for I/O and must not be available for normal physical memory.
→ The reservation may be permanent, or temporary (as achieved via bank switching).
Correct Answer: B
Question 16 Explanation:
→ Memory-mapped I/O uses the same address space to address both memory and I/O devices.
→ The memory and registers of the I/O devices are mapped to (associated with) address values.
→ So when an address is accessed by the CPU, it may refer to a portion of physical RAM, or it can instead refer to the memory of the I/O device. Thus, the CPU instructions used to access the memory can also be used for accessing devices.
→ Each I/O device monitors the CPU’s address bus and responds to any CPU access of an address assigned to that device, connecting the data bus to the desired device’s hardware register.
→ To accommodate the I/O devices, areas of the addresses used by the CPU must be reserved for I/O and must not be available for normal physical memory.
→ The reservation may be permanent, or temporary (as achieved via bank switching).
→ The memory and registers of the I/O devices are mapped to (associated with) address values.
→ So when an address is accessed by the CPU, it may refer to a portion of physical RAM, or it can instead refer to the memory of the I/O device. Thus, the CPU instructions used to access the memory can also be used for accessing devices.
→ Each I/O device monitors the CPU’s address bus and responds to any CPU access of an address assigned to that device, connecting the data bus to the desired device’s hardware register.
→ To accommodate the I/O devices, areas of the addresses used by the CPU must be reserved for I/O and must not be available for normal physical memory.
→ The reservation may be permanent, or temporary (as achieved via bank switching).