Computer Strucure

A computer system consists of five basic structural units, namely:• The unit input (Input Unit)• The control unit (Control Unit)• arithmetic and logic unit (Arithmetic & Logical Unit / ALU)• Unit memory / storage (Memory / Storage Unit)• The unit outputs (Output Unit)Control Unit and ALU form a separate unit which disebutCentral Processing Unit (CPU). The relationship between each of the units that make up a computer system can be seen in the figure below:

 

Data received via the Input Device and sent to the Memory. In the Memory data is stored and subsequently processed in the ALU. The results are stored back to memory the process prior to release via the Output Device. Control and coordination of the system is performed by the Control Unit. In summary the working principle of the computer is Input - Process - Output, known by the acronym IPO.Main functions of each unit will be explained below:• Input Unit (Input Unit)Serves to receive input (input) and then read and forwarded to the Memory / storage. In this connection, the technical term input device (input device) that is the receiver and reader input and the input media is the intermediary.• Control Unit (Control Unit)Serves to carry out supervision and control of the entire computer system. He serves as regulator of the household computer, decide the order of operations for the entire system, generating and controlling signals to control operations and adjust the flow of data from the address bus (address bus) and data bus (data bus), and to control and interpret the signals -control signals on control bus (control bus) of a computer system. Understanding of the bus can be seen at the bottom of this page.• Logic & Arithmetic Unit (Arithmetical & Logical Unit)Serves to carry out the work or arithmetic & logic calculations such as add, subtract, multiply, divide and constituent. It is also carrying out work such as data transfer, pooling of data, election data, compare data, etc., so that the ALU is a core part of a computer system. On some computer systems and help to lighten the task of the ALU of the CPU is given an additional device called a coprocessor so that in particular the process of calculation and execution of work in general to be faster. Coprocessor understanding can be seen at the bottom of this page.• Unit Memory / Storage (Memory / Storage unit)Serves to accommodate the data / programs received from units of input before processing by the CPU and also receive data when processed by the CPU which then forwarded to the output unit. In a computer system there are two kinds of memory, that naming depends on whether the device can only read or can read and write to him. Part of memory that can only be read without being able to write to her so-called ROM (Read Only Memory), while the memory can perform read and write is called RAM (Random Access Memory).• Unit Output (Output Unit)Serves to receive the results of data processing from the CPU through the memory. As with the input unit to output unit is also known term output devices (output device) and output media (output media).
 

Understanding BUS 

The bus is a group of signal path used to move bits of information from one place to another, grouped according to Standard functions of a computer system bus is the address bus (address bus), data bus (data bus) and the control bus (control bus) . Computer using a bus or a bus line as buses carrying passengers from one place to another, then the bus transporting computer data. Computer bus connects the CPU to the RAM and peripherals. All computers use the bus line for the same purpose.Understanding coprocessorCoprocessor is a microprocessor additional (auxiliary processor) to assist the task of the main processor (CPU). Actually the background of the coprocessor is intended to cover up weaknesses in math calculation and arithmetic on the Intel 8088. Its main tasks to perform mathematical calculations and arithmetic so as not to burden the Intel 8088.

Sources:1. Achmad Bachrum, PC: Know Before Purchasing, PT. Elex Press, 19912. Drs. Suyanto, MM., -, -, 199 -Computer System StructureThere is no specific provisions on how to structure a computer system. Every expert and designer of computer architecture has a view of each. However, to facilitate us to understand the details of the operating system in subsequent chapters, we need to have general knowledge about the structure of a computer system.Computer Operating SystemsIn general, the computer system comprises CPU and a device controller connected via a bus that provides access to memory. Generally, each device controller is responsible for a hardware spesisfik. Each device and the CPU can operate concurrently to gain access to memory. The existence of some hardware can cause synchronization problems. Therefore, to prevent a memory controller is added to synchronize the memory access.

General Computer Architecture

 At a more advanced computer system, its architecture is more complex. To improve performance, use multiple buses. Each bus is a data path between several different devices. In this way the RAM, processor, GPU (AGP VGA) connected by high-speed primary bus is better known as the FSB (Front Side Bus). While other slower devices connected by a lower-speed bus that connects with another bus which is faster up to the main bus. For communication between the bus is used a bridge. The responsibility of the synchronization bus that indirectly also affect the memory synchronization is done by a bus controller, otherwise known as a bus master. The bus master will control the flow of data up to at one time, the bus contains only data from one device. In practice the bridge and the bus master is incorporated in a chipset.

  Modern PC architecture

 NB: GPU = Graphics Processing Unit; AGP = Accelerated Graphics Port; HDD = Hard Disk Drive: FDD = Floppy Disk Drive; FSB = Front Side Bus: USB = Universal Serial Bus; PCI = Peripheral Component Interconnect; RTC = Real Time Clock; PATA = Parallel Advanced Technology Attachment; SATA = Serial Advanced Technology Attachment; ISA = Industry Standard Architecture; IDE = Intelligent Drive Electronics / Integrated Drive Electronics; MCA = Micro Channel Architecture; PS / 2 = A port was built to connect the mouse to the IBM PC ;If the computer is turned on, which is known as booting, the computer will run the bootstrap program is a simple program that is stored in ROM as a chip CMOS (Complementary Metal Oxide Semiconductor). Modern CMOS chips are usually of type EEPROM (electrically erasable programmable read only memory), which is non-volatile memory (not erased when power is turned off) which can be written and erased with electronic pulses. Then bootsrap program is better known as BIOS (Basic Input Output System).Bootstrap main program, which is usually located on the motherboard will examine the major hardware and hardware-initialization of the program in hardware known as firmware.Bootstrap main program will then locate and load the operating system kernel into memory and then proceed with the program here operasi.Dari system initialization the operating system will wait for certain events. This incident will determine what will be done next operating system (event-driven).This event on modern computers are usually characterized by the emergence of software or hardware interrupt, so the Operating System is called the Interrupt-driven. Interrupt of hardware is usually delivered via a particular signal, while the software sends an interrupt by invoking the system call or also known as monitor call. System / Monitor this call will cause the trap is special interrupt generated by the software due to problems or requests to the operating system services. Trap is also often referred to as the exception.Each interrupt occurs, a set of code known as the ISR (Interrupt Service Routine) will determine the action to be taken. To determine what actions to take, it can be done in two ways: a poll that makes a computer to check one by one device is there to investigate the source of the interrupt and by using the addresses stored in the array ISR known as the interrupt vector in which the system will check Interrupt Vector each time an interrupt occurs.Interrupt architecture must be able to store the address of the interrupt instruction. On older computers, this address is stored in certain places that remain, while new padakomputer, the address stored in the stack together with state information at the time.The structure of I / OThere are two kinds of action if any I / O operations. Both kinds of actions are:After the I / O starts, control returns to user program when the I / O completion (Synchronous). Wait instruction causes the CPU is idle until the next interrupt. Wait loop will occur (to wait for the next access). At most one process I / O running at one time.After the I / O starts, control returns to user program without waiting for the I / O completion (Asynchronous). System call request to the operating system to allow the user to wait until the I / O selesai.Device-status table contains the data entered for each I / O device that describes the type, address, and the circumstances. Check the operating system I / O devices to know the state of the device and turn the tables to include interrupt. If the I / O device to send / retrieve data to / from memory this is known by the name (Direct Memory Access) DMA.

The structure of I / O

 Direct Memory Access

 Used for I / O device that can move data at high speeds (close to the memory bus frequency). Device controller moves data in blocks of buffer storage directly to main memory or vice versa without the intervention of the processor. Interrupt occurs only every block instead of each word or byte data. The whole process is controlled by a DMA controller named DMA Controller (DMAC). DMA controller sends or receives signals from the memory and I / O device. The processor sends only the beginning of the address data, data destination, length data to the DMA Controller. . Interrupt the processor only occur during the transfer process is complete. The right to use the necessary memory bus DMA controller obtained with the help of a bus arbiter that the PC is now a Northbridge chipset.BusA data transfer path that connects each device on the computer. There is only one device can transmit data through a bus, but may be more than one device that reads the data bus. Consisting of two models: Synchronous bus where used but with the help of high-speed clock, but only for high-speed devices as well; Asynchronous bus used by the system but the low-speed handshake, can be used for a variety of devices.Storage StructureThe important thing to remember is that the program is part of the data.RegisterPlace some of the fruit volatile data storage that will be processed directly in the processor speed is very high. Registers are located inside the processor with a very limited number because of its function as a place of calculation / computation data



 

Cache Memory

 Temporary storage (volatile) small amounts of data to increase the speed of retrieval or storage of data in memory by a high-speed processor. Formerly stored outside the processor cache and can be added. For example the usual pipeline burst cache on the computer early 90's. However, with decreasing the die or wafer production costs and to improve performance, embedded in the processor cache. This memory is usually made based on static memory design.Random Access Memory (RAM) - Main MemoryPlace while a number of volatile data storage that can be accessed directly by the processor. Direct sense here means the processor can find the address data in memory directly. Now, the RAM can be obtained with a fairly low view of performance that can even skip the cache on an older computer.Memory ExtensionAdditional memory to be used to assist the processes in the computer, usually a buffer. Additional role of memory is often overlooked but very important for efficiency. Usually this extra memory gives a rough idea of ​​the ability of such devices, for example such as the amount of VGA memory, sound card memory.Secondary StorageStorage medium is non-volatile data that can be either Flash Drive, Optical Discs, Magnetic Disk, Magnetic Tape. This media is usually quite large carrying capacity with a relatively cheap price. Portability is also relatively higher. 

 

Figure 1-15. Disk Structure

 Structure Optical Drive

 
Storage Hierarchy

 Basic arrangement of storage systems are speed, cost, nature of volatility. Caching copying information into faster storage media; Main memory can be viewed as a last cache for secondary storage. Using high-speed memory to hold data that is accessed last. Required cache management policy. The cache also introduces another level in the storage hierarchy. This requires data to be stored together in more than one level in order to remain consistent.

 

hierarchy storage