1)Introduction to computer architecture. Organizational and methodical instructions

1.1 . Purposes and problems of studying of discipline

"the architecture of the COMPUTER" is the purpose of studying of discipline theoretical and practical preparation of students in the field of information technologies in such degree that they could choose necessary technical, algorithmic, software and technological solutions, be able to explain the principles of their functioning and it is correct to use them.

Main objectives of studying of discipline:

– formation at students of knowledge of discipline, sufficient for independent development of computing systems with new architecture;

– acquaintance with technical (equipment rooms), the software and technological solutions used for the description and development of the COMPUTER;

– development of practical skills of writing of low-level programs in assembler language, including for programming of the COMPUTERS hardware resources

The concept of the computer as a hierarchy of levels;

Hierarchy organized into orders or ranks each subordinate

to the one above it a graded or ranked series.

In a hierarchical structure there is a grouping of things into levels. There is a "top" level and then a series of lower levels under it. It's all about abstraction. At each level you describe a concept with enough detail for you to have a good feel for what lies below it.

the overall structure of the computer and its components;

The Digital (serial) Computer

The main components of a digital computer are :

• Input devices (keyboard, mouse, etc).

• Memoryboard.

• CentralProcessingUnit (processor).

• Output devices (video terminal, printer, etc.).

Besides these main components we find slow secondary storing divices, such as floppy disks and hard disks. These can contain data and programs that can be used as input. They also can receive output. Further there may be one ore more control units that check and regulates information-flow (information-traffic).basic principles of operation of computer systems.

All operating systems manage system resources.  Depending on the environment that the Operating System will work in (e.g. will it work in a lab or an office?) the way the user interacts with it is important. A graphical user interface (GUI) is much better than a Command Line Interface (CLI) for office workers as they are already familiar with it and little training is needed on the work places part.  A CLI is useful for running tests in a lab or processing data where training has already given. A CLI is a no-frill operating system (e.g. no images etc.)

2)Interrupts. Interrupts and the Instruction Cycle. Interrupt Processing. Multiprogramming.

An interrupt is a signal to the processor emitted by hardware or software indicating an event that needs immediate attention. An interrupt alerts the processor to a high-priority condition requiring the interruption of the current code the processor is executing, the current thread. The processor responds by suspending its current activities, saving its state, and executing a small program called aninterrupt handler (or interrupt service routine, ISR) to deal with the event.

An interrupt in the 8085 microprocessor is a request to stop program execution and go do something else, such as service a device request or hardware condition. The interrupt return sequence restores normal program flow to where it was interrupted.

An interrupt cycle is a memory fetch sequence generated in response to the interrupt request. It can be identified in hardware by the status lines, and the expected response is an op-code, optionally followed by immediate bytes, such as the address of a CALL instruction. Except, see interrupt types below.

Interrupt processing

The interrupt mechanism is the means for coordinating multiprogramming between an I-stream engine and the engines of a channel subsystem. An interrupt is a hardware enforced transfer of control within an I-stream engine. An interruption usually takes place after an instruction is completed and before interpretation of the next instruction is started. The logic built into z/Architecture® support is enough to preserve the information necessary to return to the interrupted point of departure. Further, interrupts of the same kind are inhibited generally by the z/TPF system, at least long enough to preserve the state of the I-stream engine and to save control information and data. Ultimately, return is made to the interrupted code without loss of data. Classes of interrupts inhibited in an I-stream engine do not prevent interrupt generating signals to be set in the device controllers and devices. These signals are essentially stacked within the channel subsystem, which presents the signals to any I-stream engine that is willing to accept the interruption.

A program status word (PSW) includes the instruction address and other information used to control instruction sequencing and to determine the state of the I-stream engine. A PSW also includes the bits used to inhibit or permit interrupts. In addition to the current PSW, which is the PSW in control of an I-stream engine, there are PSWs associated with each class of interrupts.

There are six classes of interrupts possible: External, Machinecheck, I/O, Program, Restart, Supervisor call (SVC).

Each class of interrupts is assigned an old and a new PSW. The old and new PSWs are held in the prefix area for the I-stream engine.

Multiprogramming is a rudimentary form of parallel processing in which several programs are run at the same time on a uniprocessor. Since there is only oneprocessor , there can be no true simultaneous execution of different programs. Instead, the operating system executes part of one program, then part of another, and so on. To the user it appears that all programs are executing at the same time.  If the machine has the capability of causing an interrupt after a specified time interval, then the operating system will execute each program for a given length of time, regain control, and then execute another program for a given length of time, and so on. In the absence of this mechanism, the operating system has no choice but to begin to execute a program with the expectation, but not the certainty, that the program will eventually return control to the operating system.  If the machine has the capability of protecting memory , then a bug in one program is less likely to interfere with the execution of other programs. In a system without memory protection, one program can change the contents of storage assigned to other programs or even the storage assigned to the operating system. The resulting system crashes are not only disruptive, they may be very difficult to debug since it may not be obvious which of several programs is at fault.