电脑、启动画面

电脑、启动画面 Turn on the power to start the machine is almost have to do things every day in the face of computer enthusiasts, appeared on the screen depicting the startup screen, we do not feel strange, but the computer display these screens do what work? I believe that some friends are not very clear, this article will introduce, from the power supply to the emergence of Windows blue sky white clouds, what the computer has done. First of all, let's get to know some basic concepts. The first is a very familiar BIOS (basic input and output system), and BIOS is the underlying code for dealing directly with hardware, which provides the operating system with the basic functions of controlling hardware devices. The BIOS includes a BIOS system (often say that the BIOS BIOS graphics card, motherboard) and other equipment (such as IDE controller, SCSI card or BIOS card), the BIOS system of this paper is to discuss the protagonist, because the computer's startup process is under the control of the. BIOS is generally stored in the ROM (read-only memory chip), even after the power is switched off or the power is lost. The second basic concept is the address of memory. Our machines are generally installed with 32MB, 64MB or 128MB memory, each byte of which is given an address so that CPU accesses memory. The 32MB address range with sixteen hexadecimal number is 0 ~ 1FFFFFFH, 0 ~ FFFFFH of the low-end 1MB memory is very special, because the first 8086 processor can access most memory is only 1MB, the low-end 1MB 640KB is called the primary memory, and A0000H ~ BFFFFH should be reserved for the display card memory use, C0000H FFFFFH is reserved for the use of BIOS, the BIOS system generally occupy the final 64KB or a little more space, BIOS graphics in general C0000H ~ C7FFFH, IDE controller BIOS in C8000H and CBFFFH. The first step: when we press the power switch, the power to the motherboard and other equipment of the power supply, the voltage is not stable, the control chip on the motherboard group will be sent to the CPU and maintain a RESET (reset) signal, let CPU automatically restored to its original state, but CPU at the moment will not immediately execute instructions. When the chips were detected in power supply has been a stable power supply (of course from unstable to stable process is just a momentary thing), it will be removed RESET signal (if it is to manually restart the machine, press the Reset button on the computer panel then release the button when the chip set will be removed RESET signal), CPU immediately from the address FFFF0H starts executing instructions from the front of the paper shows that this address is actually in the system BIOS address range, either Award BIOS or AMI BIOS, here's just a jump, jump to the startup code in the real system BIOS. The second step: the system BIOS boot code of the first thing to do is POST (Power On Self Test, after power on self test), POST's main task is to detect system of some key equipment and whether the existence of the normal work, such as memory and graphics and other equipment. Because POST is the earliest process of detection, This card has not been initialized, if the system is in the process of BIOS POST was found in some fatal errors, for example, found no memory or memory problems (which will only check the 640K BIOS system, so the conventional memory) will directly control the speaker sound to report an error, duration and frequency of sound represents the type of error. Normally, the POST process is going so fast that we can barely feel it, and when POST is finished, we'll call other code for more complete hardware testing. The third step: the next BIOS will find the graphics BIOS, as mentioned above, the starting address of the BIOS chip ROM storage card is usually located in C0000H, after the system BIOS to find BIOS graphics in this place is called the initialization code, the graphics BIOS to initialize graphics, the graphics are most will show some initial information in the on the screen, the graphics chip manufacturers, and other types of content, but the picture is almost flashed. The system BIOS then looks for the BIOS program for other devices and, when found, also calls the initialization code inside the BIOS to initialize the associated device. The fourth step: after looking at the BIOS of all other devices, the system BIOS displays its own boot screen, including the type of the system BIOS, the serial number, and the version number. The fifth step: then BIOS will detect and display the type of CPU and the working frequency, test all RAM started then, and at the same time show the memory test schedule on the screen, we can decide to use simple with less time-consuming or time-consuming test the type in the CMOS settings The sixth step: after the memory test system, BIOS will start some standard hardware equipment installed in the detection system, including CD, ROM, hard disk, floppy drive, serial port, parallel port equipment, in addition, the vast timing parameter of most of the newer version of the BIOS system in this process will automatically detect and set the parameters of the hard disk and memory access mode. The seventh step: standard equipment after detection system, BIOS internal PNP code will start the installation and configuration of the system in the detection of plug and play devices, after each find a device, BIOS will show the name of the device and the type of information on the screen, at the same time as the equipment allocation interrupt, DMA channel and I/O port resources. The eighth step: this step until all the hardware configuration have finished testing, most BIOS system will re clearance and at the top of the screen shows a table, which briefly lists a variety of standard hardware devices installed in the system, as well as their use of resources and some related parameters. The ninth step: next, the system BIOS will update the ESCD (Extended, System, Configuration, Data, and expand the system configuration data). ESCD is a means of system BIOS to exchange hardware configuration information with the operating system. These data are stored in CMOS (a small piece of special RAM, powered by a battery on the motherboard). In general, ESCD data is updated only when the system hardware configuration changes, So, every time we start the machine, we can see "Update ESCD"... Success "this information, however, some motherboards use BIOS system with different Windows 9x data format to save ESCD data, and Windows 9x at the start of its own process to modify the ESCD data into its own format, but the next time you start the machine, even if the hardware configuration is not changed BIOS, the system will put the ESCD data format change back, so the cycle will result in each time you start the machine, the system BIOS to update ESCD again, which is why some machines at boot time will show the reasons related information. The tenth step: after the ESCD update is finished, the startup code of the system BIOS will carry on its last work, that is, starting from the floppy disk, hard disk or CD-ROM according to the startup sequence specified by the user. To start from the C system as an example, BIOS will read and execute the main technology job technology spade spade trace Hebei Younuo Yong Zhi surname industry on the hard disk drop anchor Tuan Wo Pian Huan Zhi Liao, and each slow Huo surname sun Tuan Chi Wo Cong Muzhi technology anergy spade trace Chi technology Hebei robins Liao, dry spade, onion Pang O.SYS, this is DOS and Windows 9x the most basic file system. Windows 9x IO.SYS first to initialize some important system data, and then shows that we are familiar with the blue sky and white clouds, under this picture, Windows will continue to be part of DOS and GUI (graphical user interface) and guide the initialization part. If the system is installed to guide a variety of operating system software tools, usually the master boot record will be replaced by the software boot code, the code will allow the user to select an operating system, the basic guide code and then read and execute the operating system (the basic guide code DOS and Windows is the partition boot record). The computer is in turn on the power switch (or press Reset) to complete the initialization work to cold start, if we are under the DOS key combination occurred press Ctrl + Alt + Del (or from the Windows choose to restart your computer) to hot start, then POST will jump directly from the beginning of third another step, fifth step detection CPU and memory test will not again. We can see that both the cold start and hot start BIOS system, and again repeated that we usually do not pay attention to things, but it is a monotonous hardware detection step for us to be able to provide the basis for the normal use of the computer.