Central processor (CPU, or central processing unit - CPU; English central processing unit, CPU, literally - central processing unit) - executor of machine instructions, part hardware computer or programmable logic controller; is responsible for performing the operations specified by the programs. MP has a complex structure in the form of electronic logic circuits. Its components are:
1) ALU - an arithmetic-logical unit designed to perform arithmetic and logical operations on data and memory addresses;
2) Registers or microprocessor memory
Super-rapid memory, running at the speed of the processor, the ALU works with them;
3) CU - control unit - control of the operation of all nodes of the MP by generating and transmitting to its other components control pulses coming from
quartz clock generator, which, when the PC is turned on, begins to vibrate with
constant frequency. These fluctuations set the pace for the entire motherboard; The processor communicates with other devices (RAM) using data, address, and control buses. The bus width is always a multiple of 8 (it is clear why, if we are dealing with bytes), it is variable in the course of the historical development of computer technology and is different for different models, and is also not the same for the data bus and the address bus.
The data bus width indicates how much information (how many bytes) can be transferred at a time (per clock). The maximum amount of RAM with which the processor can work at all depends on the width of the address bus.
The power (performance) of the processor is affected not only by its clock frequency and the width of the data bus, but also the size of the cache memory is also important.
Processor Specifications:
1 .Clock frequency is the number of operations that the processor can perform per second. The unit of measurement is MHz and GHz (megahertz and gigahertz). 1 MHz means that the processor can perform 1 million operations per second, if the processor is 3.16 GHz - hence it can perform 3 Billion 166 million operations in 1 second.
There are two types of clock frequency - internal and external.
Internal clock frequency is the clock frequency at which work is done inside the processor.
External clock or system bus frequency is the clock frequency
which data is exchanged between the processor and the computer's RAM.
Until 1992, in processors, the internal and external frequencies coincided, and in 1992, Intel introduced the 80486DX2 processor, in which the internal and external frequencies were different.
The internal frequency was 2 times greater than the external one. Two types of such processors were released with frequencies of 25/50 MHz and 33/66 MHz, then Intel released the 80486DX4 processor with triple the internal frequency (33/100 MHz).
In modern processors, for example, at a processor clock speed of 3 GHz, the system bus frequency is 800 MHz.
2 .Another main characteristic of a processor is its bit depth..
The bitness of the processor is determined by the bitness of its registers.
A computer can operate simultaneously with a limited set of information units. This set depends on the width of the internal registers. A digit is a storage unit of information. In one working cycle, the computer can process the amount of information that can fit in the registers. If the registers can store 8 units of information, then they are 8-bit, and the processor is 8-bit; if the registers are 16-bit, then the processor is 16-bit, and so on. The larger the processor capacity, the large quantity information it can process in one clock cycle, which means that the faster the processor works.
The Pentium 4 processor is 32-bit. Now more and more processors are 64-bit.
3. CPU cache- a rather important parameter. The larger it is, the more data is stored in special memory, which speeds up the processor. The processor cache contains data that may be needed in the very near future. So that you do not get confused in cache levels, remember one property: the first level cache is the fastest, but the smallest, the second one is slower, but larger, and the third level cache is the slowest and largest (if any)
4. Technical process (sometimes they write technology)- not the main characteristic of the processor for the average layman, but you need to know about it in order to understand abstruse articles on computer sites. The fewer the process, the better, as they say. In fact, this is the area of \u200b\u200bthe crystal on the processor. The smaller the crystals, the more they can fit, therefore increasing the clock frequency. Yes, and a smaller crystal needs less voltage, so the heat dissipation decreases, so again, you can increase the clock frequency. This chain is given as an example so that you understand how everything is interconnected. Those process may not be written in price lists, but it is almost always mentioned in reviews.
5.Socket- this parameter is needed to standardize all processors by connectors for connecting to motherboard. For example, Socket LGA775 - if you meet such a characteristic on a motherboard, then only processors labeled Socket LGA775 and no others will fit it. The reverse rule also applies.
The interface system is:
Control bus (SHU) - designed to transmit control pulses and synchronize signals to all PC devices; - address bus (ShA) - designed to transfer the address code of a memory cell or an I / O port external device;
Data bus (SD) - designed for parallel transmission of all digits of the numeric code; - power bus - for connecting all PC units to the power supply system.
The interface system provides three directions for information transfer:
Between MP and RAM;
Between MP and I/O ports of external devices;
Between RAM and I/O ports of external devices.
Information is exchanged between devices and the system bus using ASCII codes.
Memory
Memory is a device for storing information in the form of data and programs. Memory is primarily divided into internal (located on the system board) and external (located on various external media information).
Internal memory, in turn, is divided into:
- ROM(read-only memory) or ROM (read only memory), which contains - permanent information that is stored even when the power is turned off, which serves to test the memory and computer hardware, booting the PC when it is turned on. Recording on a special ROM cassette takes place at the PC manufacturer's factory and bears the features of its individuality. The amount of ROM is relatively small - from 64 to 256 KB.
- RAM(random access memory) or RAM (random access memory), is used for the operational storage of programs and data that is stored only for the duration of the PC. It is volatile, when the power is turned off, information is lost. The OP is distinguished by special functions and access specifics:
o OP stores not only data, but also the executable program;
o MP has the ability to directly access the OP, bypassing the I/O system.
Cache - has a short access time, serves for temporary storage of intermediate results and the contents of the most frequently used cells of the OP and registers
The logical organization of memory - addressing, data placement is determined by the software installed on the PC, namely the OS.
external memory. External memory devices are very diverse. The proposed classification takes into account the type of media, i.e. a material object capable of storing information.
Tape drives historically appeared earlier than magnetic disk drives. Bobbin drives are used in supercomputers and mainframe.
Disks refer to media with direct access, i.e. the PC can access the track on which the section with the required information begins or where you want to write new information, directly.
Magnetic disks(MD) - as a storage medium, magnetic materials with special properties are used that allow fixing two directions of magnetization. Rarely used today.
HDD or "hard drives" are made of aluminum alloys or ceramics and covered with ferrolacquer, together with a block of magnetic heads are placed in a hermetically sealed case. Due to the extremely dense recording, the capacity of drives reaches several gigabytes, the performance is also higher than that of removable drives (due to an increase in the rotation speed, since the disk is rigidly fixed on the rotation axis). The first model appeared at IBM in 1973. It had a capacity of 16 KB and 30 tracks / 30 sectors, which coincided with the caliber of the popular 30 "730" Winchester shotgun.
Each HDD goes through a low-level formatting procedure - service information is written to the media, which determines the layout of the disk cylinders into sectors and numbers them, bad sectors are marked to exclude them from the disk operation process. The PC has one or two drives. One hard drive can be divided using a special program into several logical drives and work with them as with different hard drives.
GCD(optical disc drives) laser optical discs or compact discs (CD, DVD). In a PC optical drive, this track is read by a laser beam. Due to the extremely dense recording, they have a capacity of up to 8 GB.
Flash memory- a kind of solid-state semiconductor non-volatile rewritable memory (PEPROM).
It can be read any number of times (within the data storage period, typically 10-100 years), but such memory can only be written to a limited number of times (maximum - about a million cycles). Flash memory is common and can withstand about 100,000 write cycles, much more than a floppy disk or CD-RW can handle.
The main parameters of the processors are:
clock frequency,
bit depth,
operating voltage,
internal clock multiplier,
cache size.
Clock frequency determines the number of elementary operations (cycles) performed by the processor per unit of time. Clock frequency modern processors measured in MHz (1 Hz corresponds to one operation in one second, 1 MHz = 106 Hz). The higher the clock speed, the more instructions the processor can execute, and the greater its performance. The first processors that were used in PCs operated at a frequency of 4.77 MHz, today the operating frequencies of modern processors reach 2 GHz (1 GHz = 103 MHz).
Bit depth The processor indicates how many bits of data it can receive and process in its registers in one clock cycle. The bitness of the processor is determined by the bitness of the command bus, that is, the number of conductors in the bus through which commands are transmitted. Modern processors of the Intel family are 32-bit.
Working voltage processor provided motherboard, that's why different brands processors correspond to different motherboards. The operating voltage of the processors does not exceed 3 V. Reducing the operating voltage makes it possible to reduce the size of the processors, as well as to reduce the heat dissipation in the processor, which makes it possible to increase its performance without the threat of overheating.
Internal Clock Multiplier is the factor by which the motherboard clock speed should be multiplied to reach the processor frequency. The processor receives clock signals from the motherboard, which, for purely physical reasons, cannot work on such high frequencies ah, like a processor. Today, the clock frequency of motherboards is 100-133 MHz. To obtain higher frequencies, the processor internally multiplies by a factor of 4, 4.5, 5 or more.
cache memory. The exchange of data within the processor is much faster than the exchange of data between the processor and RAM. Therefore, in order to reduce the number of accesses to RAM, the so-called super-rapid or cache memory is created inside the processor. When the processor needs data, it first accesses the cache, and only when the necessary data is missing does it access the main memory. The larger the cache, the more likely it is that the data you need is there. Therefore, high-performance processors have increased cache memory.
There are cache memory of the first level (runs on the same chip with the processor and has a volume of about several tens of KB), the second level (runs on a separate chip, but within the boundaries of the processor, with a volume of one hundred or more KB) and the third level (runs on separate high-speed microcircuits located on the motherboard and has a volume of one or more MB).
During operation, the processor processes the data in its registers, RAM and external ports of the processor. Part of the data is interpreted as actual data, part of the data is interpreted as address data, and part is interpreted as commands. The set of various instructions that a processor can execute on data forms a system of processor instructions. The larger the instruction set of the processor, the more complex its architecture, the longer the instruction record in bytes, and the longer the average duration of instruction execution.
The Intel processors used in IBM joint PCs have more than a thousand instructions and are referred to as extended instruction set processors - CISC-processors (CISC - Complex Instruction Set Computing). In contrast to CISC processors, processors of the architecture have been developed RISC with a reduced instruction set (RISC - Reduced Instruction Set Computing). With this architecture, the number of instructions is much smaller, and each instruction is executed faster. Thus, programs consisting of simple instructions run much faster on RISC processors. The reverse side of the abbreviated command system is that complex operations have to be emulated by a far from always effective sequence of simpler commands. Therefore, CISC processors are used in general-purpose computer systems, while RISC processors are used in specialized ones. For the IBM PC platform, Intel's CISC processors are dominant, although recently AMD has been manufacturing AMD-K6 family processors that have a hybrid architecture (the internal core of these processors is made according to the RISC architecture, and the external structure - according to the CISC architecture).
IBM PC computers use processors developed by Intel or compatible processors from other companies that belong to the x86 family. The ancestor of this family was the 16-bit Intel processor 8086. Subsequently, Intel 80286, Intel 80386, Intel 80486 processors were produced with modifications, different models Intel Pentium, Pentium MMX, Pentium Pro, Pentium II, Celeron, Pentium III. latest model Intel is the Pentium IV processor. Other processor manufacturers include AMD with AMD-K6, Athlon, Duron and Cyrix models.
Tires
With other devices, and primarily with RAM, the processor is connected by groups of conductors called buses. There are three main tires:
data bus,
address bus,
command bus.
address bus. The data that is transmitted over this bus is treated as addresses of RAM cells. It is from this bus that the processor reads the addresses of the commands to be executed, as well as the data with which the commands operate. In modern processors, the address bus is 32-bit, that is, it consists of 32 parallel wires.
Data bus. This bus is used to copy data from RAM to processor registers and vice versa. In a PC based on Intel Pentium processors, the data bus is 64-bit. This means that in one cycle, 8 bytes of data are received immediately for processing.
command bus. Instructions executed by the processor come from the RAM on this bus. Commands are represented as bytes. Simple commands are embedded in one byte, but there are also commands that require two, three or more bytes. Most modern processors have a 32-bit command bus, although there are 64-bit processors with a command bus.
The buses on the motherboard are used for more than just communicating with the processor. All other internal devices of the motherboard, as well as devices that are connected to it, interact with each other using buses. The performance of the PC as a whole largely depends on the architecture of these elements.
The main bus interfaces of motherboards:
ISA(Industry Standard Architecture). Allows you to link all devices system block, and also provides easy connection of new devices through standard slots. Throughput is up to 5.5 MB/s. AT modern computers can only be used to connect external devices that do not require more bandwidth ( sound cards, modems, etc.).
EISA(Extended ISA). Extension of the ISA standard. Throughput increased to 32 MB/s. Like the ISA standard, this standard has exhausted its capabilities and in the future the release of boards that support these interfaces will cease.
VLB(VESA Local Bus). VESA local bus interface. The local bus connects the processor to RAM, bypassing the main bus. It operates at a higher frequency than the main bus, and allows you to increase the data transfer rate. Later, an interface for connecting a video adapter was "embedded" into the local bus, which requires increased bandwidth, which led to the emergence of the VLB standard. The bandwidth is up to 130 MB/s, the operating clock frequency is 50 MHz, but it depends on the number of devices connected to the bus, which is the main drawback of the VLB interface.
PCI(Peripheral Component Interconnect). An external device connection standard introduced with Pentium-based PCs. At its core, this is a local bus interface with connectors for connecting external components. This interface supports bus speeds up to 66 MHz and provides performance up to 264 MB / s regardless of the number of connected devices. An important innovation of this standard is the support for the plug-and-play mechanism, the essence of which is that after physical connection external device to the PCI bus connector, the device is automatically configured.
FSB(Front Side Bus). Starting with the Pentium Pro processor, a special FSB bus is used to communicate with RAM. This bus operates at a frequency of 100-133 MHz and has a throughput of up to 800 MB/s. The FSB frequency is the main parameter, it is indicated in the motherboard specification. The only thing left behind the PCI bus is the function of connecting new external devices.
AGP(Advanced Graphic Port). Special bus interface for connecting video adapters. Developed due to the fact that the PCI bus parameters do not meet the performance requirements of video adapters. The frequency of this bus is 33 or 66 MHz, the throughput is up to 1066 MB/s.
USB(Universal Serial Bus). The Universal Serial Bus standard defines new way interaction of the computer with peripheral equipment. It allows you to connect up to 256 different devices with a serial interface, and devices can be connected in a chain. The performance of the USB bus is relatively low at 1.55 Mbps. Among the advantages of this standard, it should be noted the ability to connect and disconnect devices in "hot mode" (that is, without rebooting the computer), as well as the ability to combine several computers in simple network without the use of special hardware and software.
Inner memory
Under internal memory understand all kinds of storage devices located on the motherboard. These include RAM, read-only memory, and non-volatile memory.
OperationalmemoryRAM (Random Access Memory)
RAM memory is an array of crystalline cells capable of storing data. It is used for the rapid exchange of information (commands and data) between the processor, external memory and peripheral systems. From it, the processor takes programs and data for processing, and the results are written to it. The name "fast" comes from the fact that it is very fast and the processor does not have to wait when reading data from memory or writing. However, the data is saved only temporarily when the computer is turned on, otherwise it disappears.
According to the physical principle of operation, dynamic memory is distinguished DRAM and static memory SRAM.
Dynamic memory cells can be represented as microcapacitors capable of accumulating an electric charge. Disadvantages of DRAM memory: slower data writing and reading, requires constant recharging. Advantages: ease of implementation and low cost.
Static memory cells can be represented as electronic microelements - flip-flops consisting of transistors. The trigger does not store the charge, but the state (on/off). Benefits of SRAM: Significantly faster performance. Disadvantages: technologically more complex manufacturing process, and, accordingly, high cost.
Dynamic memory chips are used as main RAM, and static memory chips are used for cache memory.
Each memory cell has its own address, expressed as a number. Modern PCs based on Intel Pentuim processors use 32-bit addressing. This means that there are 232 independent addresses in total, which means that the possible address space is 4.3 GB. However, this does not mean that just how much RAM can be in the system. The memory size limit is determined by the motherboard chipset and is typically a few hundred megabytes.
RAM in a computer is located on standard sockets, which are called modules. RAM modules are inserted into the appropriate slots on the motherboard. Structurally, memory modules have two executions - single-row ( SIMM - modules) and two-row ( DIMMs - modules). On computers with Pentium processors single-row modules can only be used in pairs (the number of connectors for their installation on the motherboard is always even). DIMM - modules can be installed one at a time. It is not possible to combine different modules on the same board.
The main characteristics of RAM modules:
memory size,
access time.
SIMM - modules have a volume of 4, 8, 16, 32, 64 megabytes; DIMM - modules - 16, 32, 64, 128, 256, 512 MB. Access time indicates how long it takes to access memory locations, the smaller the better. Measured in nanoseconds. SIMM - modules - 50-70 ns, DIMM - modules - 7-10 ns.
ROM (Read Only Memory)
When the computer is turned on, there is no data in its RAM, because RAM cannot store data when the computer is turned off. But the processor needs commands, including immediately after switching on. Therefore, the processor goes to a special starting address, which it always knows, for its first instruction. This address points to memory, which is commonly referred to as read-only memory (ROM) or read-only memory (ROM). The ROM chip is capable of storing information for a long time, even when the computer is turned off. They say that the programs that are in the ROM are "hardwired" in it - they are written there at the stage of manufacturing the microcircuit. The set of programs located in the ROM forms the basic input / output system BIOS (Basic Input Output System).
The main purpose of these programs is to check the composition and performance of the system and ensure interaction with the keyboard, monitor, hard and floppy disks.
Non-volatile CMOS memory
The operation of such standard devices as a keyboard can be serviced by BIOS programs, but it is impossible to provide such means for the robot to work with all possible devices (due to their huge variety and the presence a large number different settings). But for your work BIOS programs require all information about the current system configuration. For obvious reasons, this information cannot be stored either in RAM or permanently. Especially for this purpose, the motherboard has a non-volatile memory chip called CMOS. It differs from random access memory in that its contents do not disappear when the computer is turned off, and it differs from permanent memory in that data can be entered there and changed independently, in accordance with what equipment is included in the system.
The CMOS memory chip is constantly powered by a small battery located on the motherboard. This memory stores data about flexible and hard drives, processors, etc. The fact that the computer accurately keeps track of the date and time is also due to the fact that this information is constantly stored (and updated) in the CMOS memory. Thus, the BIOS programs read the composition data computer system from the CMOS chip, after which they can access the hard disk and other devices.
test questions
What is a motherboard? What PC components are on it?
What is the execution of programs by the central processor?
What are the main parameters of the processor? What characterizes the clock frequency and in what units is it measured?
What is cache memory? Cache levels?
What are tires for? What are the types of tires?
What motherboard bus interfaces do you know?
What is the difference between RAM and permanent memory?
What are RISC processors? What is their difference from CISC-processors?
In what memory are BIOS programs stored?
What information is stored in non-volatile memory?
What types of RAM do you know? What is the difference between them?
Informatics. Basic course. / Ed. S.V.Simonovich. - St. Petersburg, 2000
A.P. Miklyaev, Handbook for IBM PC user 3rd edition M.:, "Solon-R", 2000, 720 p.
Simonovich S.V., Evseev G.A., Murakhovsky V.I. You bought a computer: Complete Guide for beginners in questions and answers. - M.: AST-PRESS BOOK; Inforkom-Press, 2001. - 544 p.: ill. (1000 tips).
Kovtanyuk Yu.S., Solovyan S.V. Tutorial for work on personal computer- K.: Junior, 2001.- 560s., ill.
External memory is memory implemented in the form of external, relative to the motherboard, devices with different principles storage of information and types of media designed for long-term storage of information. In particular, everything is stored in external memory software computer. External memory devices can be placed both in the computer system unit and in separate cases. Physically, external memory implemented in storage. Drives are storage devices designed for long-term (which does not depend on power supply) storage of large amounts of information. The capacity of drives is hundreds of times greater than the capacity of RAM, or even unlimited when it comes to drives with removable media.
The drive can be considered as a combination of the carrier and the corresponding drive. There are drives with removable and permanent media. A drive is a combination of a read-write mechanism with the corresponding electronic circuits management. Its design is determined by the principle of operation and the type of carrier. The media is the physical medium for storing information. appearance can be disk or tape. According to the principle of storage, magnetic, optical and magneto-optical media are distinguished. Tape media can only be magnetic; disk media uses magnetic, magneto-optical and optical methods of writing and reading information.
The most common are magnetic disk drives, which are divided into hard disk drives(HDD) and floppy disk drives(NGMD), and optical disc drives, such as CD-ROM, CD-R, CD-RW, and DVD-ROM drives.
Hard Disk Drives (HDD)
The HDD is the main device for long-term storage of large amounts of data and programs. Other names: hard drive, hard drive, HDD (Hard Disk Drive). Externally, the hard drive is a flat, hermetically sealed box, inside of which there are several rigid aluminum or glass plates of a round shape on a common axis. The surface of any of the disks is covered with a thin ferromagnetic layer (a substance that reacts to an external magnetic field), in fact, the recorded data is stored on it. In this case, the recording is carried out on both surfaces of each plate (except for the outer ones) using a block of special magnetic heads. Each head is above the working surface of the disk at a distance of 0.5-0.13 microns. The disk pack rotates continuously and at a high frequency (4500-10000 rpm), so mechanical contact between the heads and disks is unacceptable.
Recording data in the hard disk is carried out as follows. When changing the strength of the current passing through the head, there is a change in the intensity of the dynamic magnetic field in the gap between the surface and the head, which leads to a change in the stationary magnetic field of the ferromagnetic parts of the disk coating. The read operation occurs in reverse order. The magnetized particles of the ferromagnetic coating are the cause of the electromotive force of self-induction of the magnetic head. The electromagnetic signals that arise in this case are amplified and transmitted for processing.
The work of the hard drive is controlled by a special hardware-logical device - the controller hard drive. In the past, this was a separate daughter board that was connected via slots to the motherboard. In modern computers, the functions of the hard disk controller are performed by special microcircuits located in the chipset.
A drive can have up to ten disks. Their surface is divided into circles, which are called tracks (track). Each track has its own number. Tracks with the same numbers located one above the other on different disks form a cylinder. The tracks on the disc are divided into sectors (numbering starts from one). The sector occupies 571 bytes: 512 are reserved for recording the necessary information, the rest are for the header (prefix), which determines the beginning and number of the section, and the end (suffix), where the checksum is written, which is needed to check the integrity of the stored data. Sectors and tracks are formed during disk formatting. Formatting is performed by the user using special programs. No information can be written to an unformatted disc. HDD can be broken down into logical drives. This is convenient because having multiple logical drives makes it easier to structure the data stored on the hard drive.
There are a huge number of different models hard drives many companies such as Seagate, Maxtor, Quantum, Fujitsu, etc. To ensure the compatibility of hard drives, standards have been developed for their characteristics, which determine the range of connecting conductors, their placement in adapter connectors, and the electrical parameters of signals. Common are the IDE (Integrated Drive Electronics) or ATA interface standards and the more productive EIDE (Enhanced IDE) and SCSI (Small Computer System Interface). The characteristics of the interfaces through which hard drives are connected to the motherboard largely determine the performance of modern hard drives.
Among other parameters that affect the performance of the HDD, the following should be noted:
disk speed- in our time, EIDE drives are produced with a rotation frequency of 4500-7200 rpm, and SCSI drives - 7500-10000 rpm;
cache capacity- in all modern disk drives a cache buffer is installed that speeds up data exchange; the larger its capacity, the higher the probability that the cache will contain the necessary information that does not need to be read from disk (this process is thousands of times slower); cache buffer capacity different devices can vary from 64 KB to 2 MB;
average access time- time (in milliseconds) during which the block of heads is shifted from one cylinder to another. Depends on actuator design and is approximately 10-13 milliseconds;
delay time- this is the time from the moment the block of heads is positioned on the desired cylinder to the positioning of a specific head on a specific sector, in other words, this is the search time for the desired sector;
exchange rate- determines the amount of data that can be transferred from the drive to the microprocessor and vice versa for certain periods of time; maximum value this parameter is equal to the bandwidth of the disk interface and depends on which mode is used: PIO or DMA; in PIO mode, data exchange between the disk and the controller occurs with direct participation CPU, the larger the PIO mode number, the higher the exchange rate; operation in DMA (Direct Memory Access) mode allows you to transfer data directly to RAM without the participation of the processor; data transfer rate in modern hard drives fluctuates in the range of 30-60 MB / s.
Floppy disk drives (FDD)
floppy drive or floppy drive is built into the system unit. Flexible media for NGMD are produced in the form of floppy disks (another name is floppy disk). Actually, the carrier is a flat disc with a special, fairly dense film coated with a ferromagnetic layer and placed in a protective envelope with a movable shutter in the upper part. Floppy disks are used mainly for the rapid transfer of small amounts of information from one computer to another. Data recorded on a floppy disk can be protected from being erased or overwritten. To do this, you need to move the small protective latch at the bottom of the floppy disk so that an open window is formed. In order to enable recording, this slide must be moved back and the window closed.
The front panel of the drive is displayed on the front panel of the system unit, it has a pocket closed with a shutter, where a floppy disk is inserted, a button for removing the diskette and an indicator light. The floppy disk is inserted into the disk drive with the top latch forward, it must be inserted into the drive pocket and smoothly pushed forward until it clicks. The correct insertion direction of the floppy disk is marked with an arrow on the plastic case. To remove a floppy disk from the drive, you need to press its button. The light indicator on the drive indicates that the device is busy (if the light is on, it is not recommended to remove the floppy disk). Unlike a hard disk, a floppy disk drives only when a read or write command is given; at other times, it is at rest. The read-write head during operation mechanically contacts the surface of the floppy disk, which leads to rapid wear of the floppy disk.
As in the case of a hard disk, the surface of a floppy disk is divided into tracks, which in turn are divided into sectors. Sectors and tracks are obtained when a floppy disk is formatted. The floppy disks are now shipped formatted.
The main parameters of a floppy disk are the technological size (in inches), recording density and total capacity. The sizes distinguish between 3.5-inch floppy disks and 5.25-inch floppy disks (now no longer used). Recording density can be simple SD (Single Density), double DD (Double Density) and high HD (High Density). The standard capacity of a 3.5-inch floppy disk is 1.44 MB, 720 KB floppy disks can be used. 3.5-inch high-density HD floppy disks with a capacity of 1.44 MB are now the standard.
The operation of any digital computer depends on the clock frequency, which determines the quartz resonator. It is a tin container in which a quartz crystal is placed. Under the influence of an electric voltage, oscillations of an electric current occur in the crystal. This very frequency of oscillation is called the clock frequency. All changes in logical signals in any computer chip occur at certain intervals, which are called cycles. From this we conclude that the smallest unit of time for most computer logical devices is a clock cycle or, in other words, a clock frequency period. Simply put, each operation requires at least one cycle (although some modern devices manage to perform several operations in one cycle). The clock frequency, as applied to personal computers, is measured in MHz, where Hertz is one oscillation per second, respectively, 1 MHz is a million oscillations per second. Theoretically, if system bus Your computer operates at a frequency of 100 MHz, which means it can perform up to 100,000,000 operations per second. By the way, it is not at all necessary that each component of the system must perform something with each clock cycle. There are so-called idle cycles (wait loops) when the device is in the process of waiting for a response from some other device. So, for example, the work of RAM and a processor (CPU) is organized, the clock frequency of which is much higher than the clock frequency of the RAM.
Bit depth
The bus consists of several channels for the transmission of electrical signals. If they say that the bus is thirty-two bits, then this means that it is capable of transmitting electrical signals through thirty-two channels simultaneously. There is one feature here. The fact is that a bus of any declared bit depth (8, 16, 32, 64) actually has more channels. That is, if we take the same thirty-two-bit bus, then 32 channels are allocated for the transmission of the actual data, and additional channels are intended for the transmission of specific information.
Transfer rate
The name of this parameter speaks for itself. It is calculated by the formula:
clock frequency * bit width = baud rate
Let's calculate the data transfer rate for a 64-bit system bus running at a clock frequency of 100 MHz.
100 * 64 = 6400 Mbps6400 / 8 = 800 Mbps
But the resulting number is not real. In life, tires are affected by a bunch of various factors: inefficient conduction of materials, interference, design and assembly flaws, and much more. According to some reports, the difference between the theoretical data transfer rate and the practical one can be up to 25%.
The operation of each bus is monitored by specially designed controllers. They are part of the system logic set ( chipset).
isa bus
The ISA (Industry Standard Architecture) system bus has been used since the i80286 processor. The expansion slot includes a main 64-pin and an additional 36-pin connector. The bus is 16-bit, has 24 address lines, provides direct access to 16 MB of RAM. The number of hardware interrupts - 16, DMA channels - 7. It is possible to synchronize the operation of the bus and the processor with different clock frequencies. Clock frequency - 8 MHz. The maximum data transfer rate is 16 MB/s.
PCI. (Peripheral Component Interconnect bus)
In June 1992, the stage appeared new standard- PCI, whose parent was Intel, or rather the Special Interest Group organized by it. By the beginning of 1993, a modernized version of PCI appeared. In fact, this bus is not local. Let me remind you that the local bus is the bus that is directly connected to the system bus. PCI, on the other hand, uses Host Bridge (main bridge) to connect to it, as well as Peer-to-Peer Bridge (peer-to-peer bridge) which is designed to connect two PCI buses. Among other things, PCI itself is a bridge between ISA and the processor bus.
The PCI clock speed can be either 33 MHz or 66 MHz. Bit depth - 32 or 64. Data transfer rate - 132 MB / s or 264 MB / s.
The PCI standard provides for three types of boards depending on the power supply:
1. 5 Volt - for desktop computers
2. 3.3 Volts - for laptops
3. Universal boards that can work in both types of computers.
The big advantage of the PCI bus is the specification plug and Play-. In addition, in the PCI bus, any signaling occurs in a packet manner, where each packet is divided into phases. A packet begins with an address phase, which is usually followed by one or more data phases. The number of data phases in a packet can be indefinite, but is limited by a timer that determines the maximum time a device can be used by the bus. Each connected device has such a timer, and its value can be set during configuration. An arbitrator is used to organize the work of data transfer. The fact is that there can be two types of devices on the bus - the master (initiator, master, master) of the bus and the slave. The master takes control of the bus and initiates the transfer of data to the destination, i.e. the slave. Any device connected to the bus can be a master or a slave, and this hierarchy is constantly changing depending on which device has requested permission to transfer data from the bus arbiter and to whom. The chipset, or rather North Bridge, is responsible for the conflict-free operation of the PCI bus. But on the PCI life did not stop its course. The constant improvement of video cards led to the fact that the physical parameters of the PCI bus were not enough, which led to the emergence of AGP.
Of all specifications processor most famous among users is the clock speed. But, few non-specialists fully understand what it is. More detailed information about this will help to better understand the operation of computing systems. Especially when using multi-core processors that have certain features of work that are far from known to everyone, but which should be taken into account when using a computer.
For a long time, the main efforts of developers were directed precisely at increasing the clock frequency. Only recently there has been a tendency to develop and improve computer architecture, increase the amount of cache memory, the number of processor cores. However, the clock frequency of the processor is not left without attention.
What is this parameter - the clock frequency of the processor?
Let's try to figure out what "processor clock speed" is. This value characterizes the number of calculations that the processor can perform in one second. Therefore, a processor with a higher clock speed also has a higher performance, i.e. capable of performing a greater number of operations in a given period of time.
Most modern processors have clock speeds between 1 and 4 GHz. This value is defined as the product of the base frequency and some coefficient. Particularly the processor Intel Core i7 920 has a native clock frequency of 2660 Hz, which is obtained due to the base frequency of the bus 133 MHz and a factor of 20. Some manufacturers produce processors that can be overclocked to higher performance. For example, AMD's Black Edition and the K-series line by Intel. It is worth noting that, despite the importance of this characteristic, it is not decisive when choosing a computer. The clock speed only partially affects the performance of the processor.
Single-core processors have practically sunk into oblivion, and are rarely used in modern computing devices. This is due to the development of the IT industry, the progress of which never ceases to amaze. Even among specialists, one can sometimes find an erroneous opinion on how to calculate the clock speed of a processor with two or more cores. A common misconception is that the clock speed should be multiplied by the number of cores. For example, a 4-core processor at 3 GHz will have an integrated frequency of 12 GHz, i.e. 4x3=12. But this is not true.
Let's explain it in simple example . Take a pedestrian walking at a speed of 4 km / h - this is a single-core processor with a frequency of 4 GHz. And a 4-core processor with a clock speed of 4 GHz is already 4 pedestrians walking at the same speed of 4 km / h. Indeed, in this case, the speed of pedestrians is not summed up, and we cannot say that they move at a speed of 16 km / h. We are simply talking about four pedestrians walking together at a speed of 4 km/h each. The same analogy can be applied to multi-core processor. Thus, we can say that a 4-core processor with a clock speed of 4 GHz simply has four cores, each of which has the same frequency - 4 GHz. From this follows a simple and logical conclusion, the number of processor cores only affects its performance, and does not increase the total clock frequency of the computing device.