Athabasca university COMP 314 - U1C1

Athabasca university COMP 314 - U1C1 - COMP 361 Unit 1...

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COMP 361 – Unit 1 (Notes) Device Controller o Maintains some local buffer storage and a set of special-purpose registers. (10) Responsible for moving the data between the peripheral devices that it controls and its local buffer storage. (10) o Typically, operating systems have a device driver for each device controller Device Driver o Understands the device controller and presents a uniform interface to the device to the rest of the operating system. (11) Interrupt-driven I/O Operation (11) o Device driver loads the appropriate registers within the device controller. o Device controller examines the contents of these registers to determine what action to take. o Controller starts to transfer data from the device to its local buffer, and informs the device driver via interrupt when the action is complete. o The device driver then returns control to the OS, possibly returning the data or a pointer to the data if the operation was a read. o Produces high overhead costs when used with bulk data. Direct Memory Access (DMA) (11) o After setting up buffers, pointers, and counters for the I/O device, the controller transfers an entire block of data directly to or from its own buffer storage to memory, with no intervention by the CPU. o Only one interrupt is generated per block, to tell the device driver that the operation is completed, rather than one interrupt per byte. Single Processor Systems (12) o If there is only one general-purpose CPU, then the system is a single-processor system. Devices can have an I/O processor, but this does not turn the computer into a multi-processor system. Multiprocessor System (12) o Three main advantages: Increased Throughput: By increasing the number, we increase the throughput. This is not multiplied by the number of processors, however, since a certain amount of overhead is incurred in keeping all the parts working correctly. Economy of Scale: They can cost less, since they can share the same peripherals. (13) Increased Reliability: The failure of one CPU will not halt the system, only slow it down. (13) Graceful degradation is the ability to continue to provide proportional service to the level of hardware. Fault Tolerance is when they can suffer a failure of a component and still continue to run. o Asymmetrical multiprocessing Is when there is a master / slave processor relationship, where the master coordinates the actions of the slaves. (13) o Symmetrical multiprocessing (SMP) Many processors can run simultaneously, and have different workloads. One processor could sit idle, while the other is overloaded. Clustered Systems (14) o They are composed of two or more individual systems coupled together (LAN, or other fast connection). o
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This note was uploaded on 07/18/2011 for the course COMP 360 taught by Professor Dr.dunwei(grant)wen during the Spring '11 term at Open Uni..

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Athabasca university COMP 314 - U1C1 - COMP 361 Unit 1...

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