Give block diagram of DMA controller. How does the CPU initialize the DMA transfer? 5m Jun2008
A device controller need not necessarily control a single device. It can usually control multiple I/O devices. It comes in the form of an electronic circuit board that plugs directly into the system bus, and there is a cable from the controller to each device it controls. The cables coming out of the controller are usually terminated at the back panel of the main computer box in the form of connectors known as ports.
The Figure 2 below illustrates how I/O devices are connected to a computer system through device controllers. Please note the following points in the diagram:
- • Each I/O device is linked through a hardware interface called I/O Port.
- • Single and Multi-port device controls single or multi-devices.
- • The communication between I/O controller and Memory is through bus only in case of Direct Memory Access (DMA), whereas the path passes through the CPU for such communication in case of non-DMA.
Using device controllers for connecting I/O devices to a computer system instead of connecting them directly to the system bus has the following advantages:
- • A device controller can be shared among multiple I/O devices allowing many I/O devices to be connected to the system.
- • I/O devices can be easily upgraded or changed without any change in the computer system.
- • I/O devices of manufacturers other than the computer manufacturer can be easily plugged in to the computer system. This provides more flexibility to the users in buying I/O devices of their choice.
(c) What is instruction pipelining? Explain the working of instruction pipelining in RISC processor. 5
Solved program can be found on this link http://cssimplified.com/computer-organisation-and-assembly-language-programming/explain-the-working-of-the-instruction-pipelining-with-the-help-of-a-diagram-5m-dec2005