Computer Architecture - Question and answer - 3

11. What is a DMA?
Direct memory access (DMA) is a method that allows an input/output (I/O) device to send or receive data directly to or from the main memory, bypassing the CPU to speed up memory operations. The process is managed by a chip known as a DMA controller (DMAC).

12. What are the Microinstruction Formats  ?
There are multiple formats for encoding the control signals in a control word.
Horizontal Format, called Horizontal microcode
Vertical Format, called Vertical microcode
Field-encoded Format

13. What is the interrupt? explain different types of interrupt in computer architecture?
A program interrupt refers to the transfer of program control from a currently running program to another service program as a result of an external or internal generated request.
There are mainly three types of interrupts:
External interrupts: It arises due to external call from I/O devices. For e.g. I/O devices requesting transfer of data, power failure, etc.
Internal interrupts: It arises due to illegal and erroneous use of an instruction or data. For e.g. stack overflow, division by zero, invalid opcode, etc. These are also called traps.
Software interrupts: It is initiated by executing an instruction. It can be used by the programmer to initiate an interrupt at the desired point in the program.

14. What is DRAM ?
DRAM: DRAM stands for Dynamic RAM, and it is the most common type of RAM used in computers. The oldest type is known as single data rate (SDR) DRAM, but newer computers use faster dual data rate (DDR) DRAM. DDR comes in several versions including DDR2 , DDR3, and DDR4, which offer better performance and are more energy efficient than DDR. However different versions are incompatible, so it is not possible to mix DDR2 with DDR3 DRAM in a computer system.

15. What is the key difference between primary and secondary memory is speed of access ?
Primary memory includes ROM and RAM, and is located close to the CPU on the computer motherboard, enabling the CPU to read data from primary memory very quickly indeed. It is used to store data that the CPU needs imminently so that it does not have to wait for it to be delivered.
Secondary memory by contrast, is usually physically located within a separate storage device, such as a hard disk drive or solid state drive (SSD), which is connected to the computer system either directly or over a network. The cost per gigabyte of secondary memory is much lower, but the read and write speeds are significantly slower.

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