a) Basic device
What is the basic elements of a modern PC? The most "substantial" part of any computer is the system unit. Inside it are power supply board with a central processor (CPU), video card, hard disk, floppy disks and other devices for input / output. Often, video controllers and I / O located directly on the PC motherboard. In the system unit can be placed multimedia: sound card and the device reading optical discs - CD-ROM. In addition, the term "computer" includes a keyboard, mouse and monitor.
b) Microprocessors and system bus
In the IBM PC-compatible computers are used only Intel chips or their clones, with a similar architecture.
Tires. The main computer microprocessor devices connected via the so-called system bus. For this bus is not only the transfer of information, but also addressing devices, as well as the exchange of official signals. Typically, connect additional devices to the system bus is done through expansion connectors.
To connect card expansion on the system bus-based microprocessor i8088 (IBM PC and IBM PC / HT) use 62-pin connectors. In particular, this includes a system bus lines 8 and 20 address lines, which limit the address space in a computer limit
1 MB. In computers PC/AT286 became the first to apply the new system bus ISA (Industry Standart Architecture), which could pass along have 16 bits of data, but through 24 address lines directly to 16 MB of system memory. This system bus is different from the previous presence of additional Z6-contact connector for the card expansion. Computer-based microprocessors use i80386/486 have special tires for memory, thus maximize its performance. Nevertheless, some Attached connectors expand the system bus could not reach a speed of the exchange comparable to a microprocessor. Mainly concerned with the overseers of drives and video adapter. To solve this problem, the use of so-called local (local) bus, which directly link the microprocessor to the overseers of peripheral devices. In the recent past used two standard local bus: VL-bus (VESA Local-bus) and PCI (Peripheral Component Interconnect). Now virtually all new tires produced - AGP (Advanced Graphic Port) to connect devices to the tires on the computer have special connectors.
Processor. Is an essential component of any PK.Osuschestvlyaet implementation of programs on your computer and manages the work of other computer devices. The speed of its work largely determines the speed of your computer. In 1VM RS uses microprocessors developed by Intel, and sometimes - compatible with chips of other firms.
Characteristics of microprocessors. Microprocessors differ dvmya characteristics: type (model) and frequency. The most common models of Intel-80486, Pentium, Pentium MMX and Pentium II, they are in ascending order of performance and price. The same model of microprocessor may have a different clock speed - the higher clock speed, the higher the productivity and cost microprocessor.
Clock frequency determines how many basic operations (strokes) microprocessor performs in one second. Clock Speed is measured in megahertz (MHz). It should be noted that different models of microprocessors perform the same operation (for example, the addition or multiplication) for the different number of cycles. The higher the model of microprocessor, so as to be smaller strokes required to perform the same operation. So, for example, the Intel-80386 microprocessor running at two times faster than Intel-80286 with the same frequency.
Currently, the most common processor company Intel, although other PC companies (AMD, Cyrix) represent them worthy competition. Currently available processors series Pentium II, Pentium III and Pentium Celeron. At the same time, Russia has a huge park ustapevshih processors 486 and Pentium.
c) Monitors
All devices on the system bus microprocessor is considering either as addressable memory, or as input / output ports. Generally speaking, the port understand a certain pairing scheme, which typically includes one or more input / output (special memory).
On the commission of certain events microprocessor can get the signal, called the interruption. In response to this ongoing sequence of commands is suspended (suspended), but instead begins to run another sequence corresponding to this interruption. Typically, interrupts are divided into hardware, software and logic.
The hardware interrupt (IRQ) transferred to a special line system bus and are linked to requests from external devices (for example, pressing the keys on the keyboard). Logical interruption occur during the microprocessor itself (for example, division by zero), a program initiated by executing a program and are commonly used to call the special sub.
In the first IBM PC computers used by chip controller interrupt i8259 (Interrupt Controller), which has eight entrances to interrupt signals (IRQ0-IRQ7). As you know, at the same time, the microprocessor can serve only one event, and in selecting the event it helps interrupt controller, which establishes for each of its entrances to a certain level of importance - a priority. The highest priority interrupt request line is IRQ0, and the smallest - IRQ7, which is a priority decreases in order of increasing numbers of lines. In the IBM PC / AT eight lines of interruption was no longer enough and their number was increased to 15. The first models to be used cascading inclusion of two chips i8259. It was carried out by connecting the output a second controller to the door IRQ2 first.
It is important to understand that here. Lines interruption IRQ8 - IRQ15 (ie, inputs a second controller) have lower priority than IRQ1, but above IRQ3.
While direct access (DMA, Direct Memory Access) peripheral device is linked with memory directly and not through internal registers microprocessor. The most effective such transfer of data happens in situations that require high speed exchange for
Large quantities of information. To initialize the process of direct access to the system bus used by the appropriate signals.
In computers compatible with IBM PC and PC / XT, to provide direct access to the memory used by a 4-channel chip DMA i8237, channel 0 which is designed for the regeneration of dynamic memory. Channels 2 and 3 are used to control high-speed data transfer between floppy drives, hard drive and memory, respectively.
IBM PC / AT-compatible computers have a 7 channel direct memory access. The first computers, this has been achieved Cascade inclusion of two chips i8237, as in the case of Supervisors interruptions.
g) Memory Rom, Ram
All personal computers using three types of memory: rapid, continuous and external (different drives). RAM to store variable information because it allows for changing its content in the course of microprocessor
respective operations. As at any time access can be carried out to randomly selected cell, the type of memory known as well as memory with random sampling - RAM (Random Access Memory).
All programs, including games, it was performed in memory. Permanent memory usually contains such information should not be changed for a long time. Permanent memory has its own name - ROM (Read Only Memory), which indicates that it is only modes of reading and storage.
The logical organization of memory. As is known, used in IBM PC, PC / XT microprocessor i8088, through its 20 targeted Tire provides access to the 1-Mbaytnomu memory space. The first 640 kilobytes of space in reporting to the IBM PC-compatible computers are usually referred to as a standard memory (conventional memory). The remaining 384 Kbayta reserved for system use and are named in memory of the top addresses (UMB, Upper Memory Blocks, High DOS Memory, or UM Area - UMA). This area of memory reserved by positioning system ROM BIOS (Read Only Memory Basic Input Output System), under the screen and ROM-memory additional adapters.
MORE (expanded) memory. Almost all personal computers, memory UMB rarely filled completely. Empty, tended to expand the system ROM BIOS or a portion of video and the area under the additional
Modules ROM. This is based specification of additional memory EMS (Ehpanded Memory Specification), first developed by Lotus Development, Intel and Microsoft (sometimes so-called LIM-cpetsifikatsiey). This specification allows the use of RAM over the standard 640 kilobytes for applications. The principle of additional memory is based on the switching units (pages) of memory. In the UMB, between videobuferom and system RGM BIOS, is allocated unallocated 64-Kbaytnoe "window", which is divided into pages. Software and hardware can display any additional memory segment to any of the pages allocated slots (TM). While the microprocessor has always appealed to the data stored in a "window" (address below 1 MB), addresses these data can be removed for additional memory on "window" for a few megabytes of computer processor i8088 to realize additional memory should apply special fees to hardware support "swap" blocks (pages) of memory and an appropriate driver software. Of course, pay extra memory can be installed in the computer-based processors and i80286 above modules ROM. This is based specification of additional memory EMS (Ehpanded Memory Specification), first developed by Lotus Development, Intel and Microsoft (sometimes so-called LIM-cpetsifikatsiey). This specification allows the use of RAM over the standard 640 kilobytes for applications. The principle of additional memory is based on the switching units (pages) of memory. In the area of UMB, between videobuferom and system RGM BIOS, is allocated unallocated 64-Kbaytnoe "window", which is divided into pages. Software and hardware allow the display of any segment of the additional memory in any Funds from the pages of "windows". While the microprocessor has always appealed to the data stored in a "window" (address below 1 MB), addresses these data can be removed for additional memory for the "window" for a few
In a computer processor for i8088 to realize additional memory should apply special fees to hardware support "swap" blocks (pages) of memory and the corresponding software driver. Of course, pay extra memory can be installed in the computer processor-based i80286 and above.
Extended (extended) memory. Computers that use l80286 processor with 24-bit target Bus physically can address 16 MB, and in the case of processors i80386/486 - 4 GB of memory. This option is only available for protected mode processor, which is the operating system MS-DOS does not support. Expanded memory (extended) is located above the field at 1 Mb (Do not confuse 1 MB of RAM and 1 MB address space). To work with an expanded memory of the microprocessor must move from Real in protected mode and back. Unlike l80286 microprocessors i80386/486 perform this operation just why they composed of MS-DOS has a special driver - EMM386 memory manager.
By the way, if a driver memory can be expanded as additional emulate. Hardware support in this case should provide the microprocessor is not below i80386 or support a set of special chips (for example, sets NEAT firms Chips and Technologies). It should be noted that many board memory, supporting standard LIM / EMS, could be used as well as extended memory.
Cache memory. Cache memory is intended to harmonize the work of a relatively slow speed devices, such as dynamic memory with the fastest microprocessor. Using cache avoids cycles waiting in his work, which reduces the efficiency of the system.
With the help of the cache usually tries to harmonize the work of external devices, such as different drives, and microprocessor. The corresponding controller cache memory to ensure that commands and data that will be needed microprocessor at a certain time, it was so far have been in the cache.
d) Hard Drive
Hard disk drive (vinchestery) are designed for permanent storage of information used when working with computers: programs operating system, frequently used software packages, the editors of documents, compilers of programming languages, etc.
Capacity diska.Dlya user's hard disk drives do not differ notably its capacity, ie so how much information stored on the disk. Now computers mostly equipped with 520 megabytes of hard disk and more. Computers running as file servers can be equipped with a hard drive 4 - 8 MB and not one.
The speed of the disc. The speed of the disc has two indicators:
1) time access to data on the disk.
2) The speed of reading and writing data to disk.
These characteristics correspond with each other about the same as acceleration time and a maximum speed of the car. When reading or writing short blocks of data located in different parts of the disc,
Speed work is determined by time access to data - just as when driving a car around the city in peak hour with constant disperse and braking is not so important maximum speed, fostered by a car. But while reading or writing data (tens and hundreds of kilobytes) files is far more important than bandwidth tract exchange with the disc - just as when driving a car on the highway more important than the speed of the car than the acceleration time.
It should be noted that access time and speed reading - recording depend not only on the drive itself, but on the parameters of the entire tract exchange with the disk: the speed of the disk controller, the system bus and the main microprocessor computer.