What is POST power-on self-test? POST power-on self-test: After the microcomputer is turned on, a self-inspection of the system is self-inspected. This process is often referred to as POST - Power On Self Test. Almost all hardware of the system is detected.
How does POST perform self-test?
After the motherboard is turned on, the system first checks the internal devices first by the Power On Self Test, the power-on self-test program. When we press the start button (power switch), the control of the system will be completed by the BIOS. Since the voltage is still unstable, the motherboard control chipset will send an RESET (reset) signal to the CPU. The CPU is initialized while waiting for the power good signal (the power supply is ready for the power). When the power is started to stabilize (of course, from the unstable to the stable process is only a short moment), the chipset withdraws the RESET signal (if you are manually pressing the RESET button on the computer panel to restart the machine, then release the button The chipset will remove the RESET signal), and the CPU immediately starts executing instructions from the address FFF0H. This address is within the address of the system BIOS, whether it is award BIOS or Ami BIOS, put it here just a jump instruction, jump The real start code in the system BIOS. The system BIOS startup code first to do is to perform POST (Power On Self Test), due to many of the computer's hardware devices (including memory, interrupt, expanded cards), should detect whether these devices work status normal. This process is conducted one by one. BIOS vendors give each device to a test code (called Post Code, boot self-detection code), first detecting a setting, first write the corresponding Post Code 80H (address) Diagnostics port, when the device detects, then the other settings of the POST Code are sent to test this setting. If a device is not passed, this post code will remain at 80h, and the detector will stop, and the alarm is performed according to the determined alarm (BIOS vendor also defines the alarm, different settings Failure, its alarm is also different, we can distinguish the fault depending on the alarm.
Is the POST self-test to detect what order?
The POST self-testing process is roughly: Power-CPU-ROM-BIOS-SYSTEM CLOCK-DMA-64KB RAM-IRQ-Graphics, etc. Detecting the previous process before the graphics card is known to the key component test. If the key components have problems, the computer is in a suspended state, and it is used to the core failure. Another type of fault is called a non-critical fault. After the graphics card is detected, the computer will detect 64KB memory, I / O port, soft hard drive, keyboard, plug and play device, CMOS setting, etc. on the screen. Display a variety of information and error reporting. Under normal circumstances, the POST process is very fast, and we can't feel this process.
What is POST self-test code meaning?
When the system detects a corresponding error, the report is performed in two ways, that is, the error information is displayed on the screen or the detected fault is pointed out in the way the alarm sound.
CMOS Battery Failed (CMOS battery failure).
Cause: Description CMOS battery has been insufficient, please replace new batteries.
CMOS Check SUM Error-Defaults Loaded (CMOS is found when all checks are performed, so load the preset system setting value). Reason: This situation usually occurs because the battery is insufficient, so you may wish to try it first. If the problem still exists, then the CMOS RAM may have problems, it is best to return to the original process.
Display Switch Is Set IncorRectly (Display Switch Configuration Error).
Cause: The proofer on the older motherboard can set the display as monochrome or color, and this error message indicates that the settings on the motherboard and the settings in the BIOS are inconsistent, and they can be reset.
Press Esc To Skip Memory Test (Memory Check, you can press the ESC button).
Reason: If there is no settlement self-test in the BIOS, then boot will perform memory test, if you don't want to wait, press the ESC button to skip or go to the BIOS to open Quick Power On Self Test.
Hard Disk Initializing [please wait a moment ...] (hard drive is initializing, please wait for a while).
Cause: This problem is not seen on the newer hard drive. But on the old hard disk, it starts slowly, so this problem will occur.
Hard Disk Install Failure (hard disk installation failed).
Cause: The power cord of the hard disk, the data line may not be connected or the hard disk jumper is not wrong (such as the two hard drives on a data line are set to Master or Slave.)
Secondary Slave Hard Fail (detects from disk failure).
Cause: 1 CMOS is not set (for example, there is no slave plate but in CMOS) 2 hard drive power cord, the data line may not be connected or the hard disk jumper is not set.
Hard Disk (s) Diagnosis Fail (an error occurred while performing a hard disk diagnosis).
Cause: This usually represents the fault of the hard disk itself. You can first pick the hard drive to try another computer, if the problem is the same, then send it.
FLOPPY DISK (S) Fail or Floppy Disk (s) Fail (80) or FLOPPY DISK (S) Fail (40) (cannot drive floppy drive).
Cause: Is the wiring of the floppy disk or loose? Is there any power supply? If you have no problem, buy a new one.
Keyboard Error or No Keyboard Present (keyboard error or missed keyboard)
Reason: Does the keyboard cable plug? Whether the cable is damaged?
Memory Test Fail (memory detection failed)
Cause: It is usually caused by memory incompatibility or failure.
Override enable-defaults loaded (Current CMOS Settings Unable to start the system, load the BIOS preset to start the system).
Reason: It may be that you are in the BIOS settings that are not suitable for your computer (like your memory can only run 100MHz but you let it run 133MHz), then enter the BIOS setting to re-adjust.
Press Tab To show post screen (press Tab to switch screen display)
Reason: Some OEM vendors will replace the BIOS preset boot display screen with their own display screen, and this prompt is to tell the user to switch the manufacturer's custom screen and BIOS preset boot screen. .
Resuming from disk, Press Tab to show post screen (boot from hard drive, press TAB to display the boot self-test screen). Cause: The BIOS of some motherboards provides the feature of Suspend to Disk. When the user is turned off in the SUSPEND TO DISK, this prompt message is displayed next time.
BIOS ROM CHECKSUM ERROR-SYSTEM HALTED (BIOS program code is found when the sum check (Checksum), so it cannot be turned on)
Reason: This problem is usually because the BIOS program code update is not completely caused, and the solution will refresh the Bios.
Hard Disk Initizlizing [please wait a moment ...] (Initizlize) action)
Cause: This message can't be seen at all on the new hard disk. But on the older hard drive, this action will see this message because of slower.
How is the number of POST self-test bells defined?
POST power-on self-testing will also indicate the detected fault by alarm sound. However, it is necessary to note: Since the current motherboard BIOS type can be roughly divided into Award, AMI, Phoenix (Award has merged with phoenix), so different types of BIOS, the self-test error defined by the number of self-test bells is inconsistent. Therefore, it must be distinct.
Self-test alarm and meaning:
Ami BIOS
1 short memory refresh failed 2 short memory ECC compared error 3 short system basic memory (1st 64K) check failed 4 short system clock error 5 Short central processor (CPU) error 6 short keyboard controller error 7 short system real mode Error, can not switch to protection mode 8 short display memory error (display memory may be broken) 9 short ROM BIOS test and error 1 length 3 short memory error (memory damage, please replace) 1 length 8 short display test error (display data cable Sorry or display the card inserted?
Award BIOS
1 short system normal boot machine 2 short regular error, please enter the CMOS setup Reset incorrect option 1 length 1 short RAM or motherboard error 1 length 2 short display error (display or display card) 1 length 3 short keyboard controller error 1 9 short main board Flashram or EPROM error (BIOS damage) continuously respond (long-sound) memory plug instability or damage to stop power, display does not have a display card connection, repeated short-term power supply No sound No display power
Phoenix BIOS
1 short system normal boot machine 3 short system power-on self-test initialization (POST) failed 1 short 1 short 2 short motherboard error (motherboard damage, please replace) 1 short 1 short 3 short motherboard battery dead or CMOS damage 1 short 1 short 4 short ROM BIOS check error 1 short 2 short system real-time clock has problems 1 short 2 short DMA channel initialization failed 1 short 2 short 3 short DMA channel page register error 1 short 3 short memory channel Refresh error ( Problem range for all memory) 1 short 3 short 2 short volume memory error (memory corruption or RAS setting error) 1 short 3 short three short volume memory errors (most likely the memory damage on the DIMM0 slot) 1 short 4 short 1 short Basic memory first address error 1 short 4 short system basic memory (1st 64K) has parity error 1 short 4 shorts 3 short EISA bus timeout error 1 short 4 short 4 short EISA NMI port error 2 short 1 Short 1 short system basic memory (1st 64K) Check failed 3 short 1 short 1 short first DMA controller or register error 3 short 1 short 2 short second DMA controller or register error 3 short 1 short 3 short Main Interrupt Process Register Error 3 Short 1 Short 4 Short Subinter Process Register Error 3 Short 4 Short Keyboard Clock There is a problem, reset in CMOS to not installed to skip POST3 short 3 short 4 short display card RAM error or no RAM, not fatal error 3 short 4 short display data cable loose or display card insert unstable or display card damage 3 short 4 short 3 short no found display card ROOS4 short 2 short 1 short system real-time clock error 4 Short 2 short system startup error, CMOS settings or BIOS damage 4 short 2 short-key disk controller (8042) Gate A20 switch is wrong, BIOS cannot switch to protection mode 4 short 4 short 4 short protection mode interrupt Error 4 short 3 short memory errors (memory corruption or RAS setting error) 4 short 3 short system second clock error 4 short 3 short 4 short real clock error 4 short 4 short 1 short stroke port (COM port, Mouse port) fault 4 short 2 short compiled line (LPT port, print port) error 4 short 4 short 3 short digital coprocessor (8087, 80287, 80387, 80487) How do I prompt after the error? POST self-test, if there is a mistake, it will be handled in two cases: for a serious fault (fatal failure), it is stopped. At this time, because various initialization operations have not been completed, no hints or signals can be given; for non-strict failures A tips or sound alarm signal (described above) is given to wait for the user to process. With the BIOS self-test function (POST self-test), we can easily detect the failure of the motherboard to properly solve.
If we press the power button, only the power indicator is on, there is no reflection of the computer screen, and there is no alarm; then how should we solve this?
The screen is not displayed, and there is no alarm. We can't get the corresponding information from the Post self-test function; everyone knows that the computer is a complex and precise product portfolio, so there is a problem in a link, there may be no launch machine (we mainly Talk about hardware aspects). Therefore, if there is a black screen, there is no alarm sound, we should analyze the problem according to the computer's startup process.
What is the startup process of the computer?
When we press the start button, we first started should be a power supply (because if there is no power supply, all the accessories on the motherboard cannot work). However, in order to ensure safe use, the power part takes a series of safety protection measures; so the switching power supply will have a delay from the starting to stabilization, waiting for each set of voltages to stabilize, the power supply will output a detection signal. This signal indicates that the voltage is normal when this signal is normal, and these portions include input voltages and output voltages of each group. The result of these signals is a Power Good signal (also known as Power OK or PWR OK signal); if the motherboard does not accept this signal, the clock chip will continue to send a reset signal to the CPU (with us RESER RESER) Quite), the CPU will not work. Did the CPU accept normal power good signals, is the motherboard and CPU start? In fact, the motherboard is at this time, and according to the definition of the CPU's VID0-VID3 pin, send the VID0-VID3 signal provided by the CPU to the respective port of the power management module; if the motherboard BIOS has the function of setting the CPU voltage, The motherboard will generate a new VID signal with the corresponding relationship set with the VID and sent to the power management module chip. The power management module will convert it to the reference voltage according to the setting and pass the DAC voltage to the reference voltage. Pass and close, the energy is sent to the CPU through the inductor coil, and finally the output voltage is comparable to the set voltage value by the adjustment circuit.
Since the CPU also depends on the frequency supported by the motherboard frequency generator by the IC bus according to the frequency of its own; because the computer is necessary to perform the correct data transfer and normal operation, there is no clock signal, the clock signal is The main role in the circuit is synchronization; because in the data transfer process, there is a strict requirement for timing, and only this can guarantee that the data does not have an error in the transmission process. The clock signal first sets a benchmark, we can use it to determine the width of other signals, and the clock signal ensures synchronization of both parties that transceiver data. For the CPU, the clock signal is used as a reference, all signal processing inside the CPU must be used as a ruler so that it determines the execution speed of the CPU instruction; if the frequency of the CPU itself cannot adapt to the high frequency provided by the frequency generator, Unable to work properly. Therefore, only when the Power Good signal is accepted, the CPU can work normally when the corresponding clock frequency is received, and the corresponding clock frequency is, that is, the BIOS program is started.
How to determine, solve the fault?
Because if you accept the Power Good signal, the system has been processed in the RESET (reset) loop, so the motherboard can not start, the corresponding other hardware, such as the graphics card can not work, the display does not accept the signal from the graphics card, so therefore There is also no display, it is always standby. At this time, we should detect the power supply, do not think that the power light is on, it indicates that the electricity is normal, because as long as there is a signal fault (this part circuit is not normal or not stable), the input Power Good signal is low, ie Indicates that the power supply is faulty or has not yet entered the stable shape; although the power indicator is on, but since the motherboard does not accept the normal Power Good signal, it cannot be started. We detect the power supply method is to use a power supply test that works. If the power supply is ATX-type, we can use the wire to pick 13 and 14 foots, such as the power supply fan can run normally, indicating that the power supply is intact, then the fault should be on the motherboard.
After replacing the normal power, if the system still does not work, press the above motherboard launch process, test the CPU's power management module and frequency generator. However, because we cannot have a complete device to test the power and frequency modules on the motherboard (most computer enthusiasts cannot have such settings, and have corresponding detection capabilities). So we need to use the exclusion method to test the CPU on other normal motherboards. The test ruled out the CPU's fault, and the motherboard frequency setting problem should be detected. Computer enthusiasts use or test the overclocking capability of the CPU, by adjusting the outer frequency of the motherboard (current CPU has been locked, only the outer frequency can be set, and multiplier cannot be set) to adjust the operating frequency of the CPU. If the CPU cannot adapt to high operating frequency, although the power supply is supplied normally, the motherboard cannot be activated. What is the system still can't start?
If the hardware is normal (tested), then after the POST is self-detected, the CPU will start executing the instruction from the address FFFF0H. This address is within the address of the system BIOS, whether it is Award BIOS or Ami Bios, put it here. Just a jump instruction, jump to the real launch code in the system BIOS. Since the BIOS is a bridge between the operating system and the hardware, providing the lowest level, most direct hardware control, and the original operation of the computer is done in accordance with the content (instruction) cured in the BIOS (instruction). Therefore, such as BIOS file destruction or BIOS chip is damaged, it will directly affect the start of the motherboard.
How to determine whether the BIOS is corrupted?
It is difficult to determine whether the BIOS is normal, because if there is no test tool such as a programmer; it is unable to judge whether the BIOS file or chip is normal. For ordinary users, it is only looking for a maintenance business.
If the screen shows the Bios Rom Checksum Error-System Halted (BIOS Program Code) When you find an error when checking (Checksum), you should read the BIOS, the sum check, there is no machine. This problem is usually because the BIOS program code update is not completely caused, and the solution re-writes the Bios Bios.
What is the BIOS Checksum checkout?
Checksum is a simple and easy integrity control method in the field of data processing and data communication. Combine all bytes of the data through a series of arithmetic or logical operations to get a checksum value. The checksum values can be calculated by the same method and compared to the value calculated last time. If the phase is equal, the data has not changed; if it is not equal, the data has been modified.
Other reasons why the system can't start?
Normally, after the BIOS is transferred, the inspection of the computer is turned on, the initialization system device, the instruction to load the operating system, and the operating system is sent to the hardware, and some hardware detection can also pass POST. The test shows whether the work is normal, and some problems before the boot can be solved. In fact, because after the CPU is transferred into the BIOS, it also needs to detect 640K's basic memory and interrupts of the slots. Although the memory error POST can be prompted to prove us, if the internal memory is damaged or short, it will cause the motherboard part. Short-circuit, or can't start the machine; therefore, for the system no display, no alarm processing, in addition to substantially excluding mode, it is necessary to accumulate usa.
Due to overclocking, the machine cannot be started, how should I solve?
There are two ways to clear the frequency setting of overclocking; one is to clear CMOS settings (for setting a CPU operating frequency in CMOS); as long as the CMOS clear jumper is found on the motherboard (in general on the motherboard battery Next, a three-needle jumper), after clearance of CMOS, resume the jumper position, you can solve it. Another way is to reset the frequency setting jumper (a way to set the CPU frequency through the motherboard frequency jumper), as long as the normal frequency is reset as the manual. What is the test tool?
The motherboard detector card is a professional hardware fault detection device that reads the POST CODE in the 80H address using its own hardware circuit, and is decoded by the decoder. Finally, the code is displayed one by one by the digital LED indicator. The principle is consistent with the POST self-test. This will determine the problem in the part of the hardware by the 16 credit code displayed on the DEBUG card, without having to rely on the computer motherboard, and a monotonous warning sound is roughly judged. And since the detection diagnosis card is used to read the POST code of the diagnostic port, it is not subject to the main board BIOS chip, and it can be diagnosed in the case of the motherboard BIOS; and use the detection card itself The secondary tube is to display the voltage working state of each group. Through it, it is known that the hardware detection is not passed by memory or CPU, or other hardware, it is convenient to solve the tricky motherboard problem.
The current motherboard detection card usually has two interfaces of ISA and PCI. It can be convenient to use any of the motherboards, and it will not burn the motherboard or detection card (very suitable for primary users) after insertion. Bit Digital LDE Tips; If the computer is inserted into the corresponding slot of the failed motherboard, after the power is turned on, according to the last stagnation manual of the LED indicator, refer to the fault list manual with the card, you can know the motherboard failure. The location. And the latest detection card, can run the detection lamp by the main board of the quotation, which is convenient to detect the fault of the motherboard itself, or the failure of other hardware on the motherboard.
How to use the motherboard to detect acknowledgment card?
First, insert the Debug card on the faulty motherboard, CPU, memory, expansion cards, do not plug, only the power supply of the motherboard, at this time, the main system should be bright, otherwise the motherboard does not control; the reset signal should be bright after half a second Off, if it is not bright, the motherboard does not reset the signal and cannot be used. If it is always on, the motherboard is always in the reset state, and it cannot be performed down. The beginner often puts the accelerator switch line as a reset line to the reset pin, resulting in reset The lamp is often bright, and the reset circuit is damaged will also cause this malfunction; the divided signal light should be on, otherwise the crossover portion is faulty; 5V, -5V, 12V, -12V (new card is 3V, -3V) four The (six) power indicator should be bright enough, no brightness or brightness is not enough, indicating that the switching power supply output is not normal, or the motherboard shorts or opens the power supply; the BIOS signal is not bright, but if inserted into intact After the CPU, the BIOS light should be no rule, otherwise the CPU is bad or the jumper is incorrect or the motherboard is damaged. This feature of Debug 2000 is quite effective, and the voltage value of -5V, -12V is rarely used in the PC component, and has a newly or useful PC power supply. Its -5V and -12V may have been damaged. I have no things, but I will let you headache, now, it is convenient to solve this problem through the DEBUG card. After the above simple fault is excluded, insert the relevant expansion card (generally only the minimum system), depending on the code displayed after the boot, you can directly find the problematic accessories, so that the hardware error that occurs when the installed is easily resolved. For example, hardware such as memory, graphics card, CPU, the function error of the BIOS, CPU cache, etc. Why can't you start your computer using a USB disk?
This is mainly due to the fact that the USB start option at the BIOS is open or the end is properly set. After entering the CMOS setting, in the system boot order, there are "FDD USB" and "HDD USB" options, which is the USB boot option, so the option system startup order is set first. But some old motherboards do not support USB startup, so it is not possible to use flash.
How to use a USB mobile hard drive to boot your computer?
To start your computer with a USB hard drive, you must have the motherboard itself to support the USB setting start; the current USB starts mainly USP-FDD, USB-ZIP, USB-HDD, and USB-CDROM. To use a USB mobile hard disk as a boot disk, you must set the system boot order to USB-HDD in the CMOS settings.
Why can't my new motherboard can't find IDE settings? How should I solve?
This is due to the fact that the capacity and speed of the current hard disk are constantly improving, regardless of power consumption, the requirements of the power supply, and the hard disk is turned from the power off to the startup (Power ON) to the initialization, it takes time Increased, but the main board BIOS is executed from the boot to the detected IDE device, which causes the motherboard to not detect the hard disk or delay the time of detecting other IDE devices because the hard disk is time consumption, especially This problem is even more pronounced on two or more hard disk systems connected to two or more, if the reset reset button is pressed, the fault is no longer appearing because each IDE device has completed initialization. For this, simply enter the CMOS Setup interface as long as it is turned on, find the "Boot Delay Time" option (Note: Some vendors' BIOS is "IDE DELAY TIME"), and the delay time is appropriately extended. For motherboard BIOs without this option, you can also set the memory self-inspection to three times in the CMOS Setup option and open the FLOY SEEK, add the IDE initialization time. Why does the new hard disk do not match, is it a BIOS setting?
This is a normal imaging, mainly due to the calculation method of the hard disk manufacturer and the calculation method of the operating system. In general, the hard disk manufacturer is in 1k = 1000bit, and the operating system is 1k = 1024bit, thus there will be an error in the capacity.
The computer is often restarted, and when it occurs when reading the disk, is it related to BIOS?
It should be independent of the BIOS setting, mainly due to insufficient power supply, causing voltage fluctuation; because some of the poor power supply is normal in the air-load, but due to insufficient power supply, a load (when reading the hard disk, It takes a lot of working current, and the voltage will fall, thus causing restart. Replace a high quality, high power power supply can be resolved.
After setting CMOS, why is memory need to be detected three times?
In fact, it is mainly to close "Quick Boot" in the BIOS setting, as long as entering the CMOS setting, in Quick Power On Self Test, set it to "Enable" to open it.
Why show "DIMM 3 & 4 Conflict.Turn Off Power and Remove Dimm 4" prompt?
This prompt is generally after upgrading memory, mainly due to the main board's third and fourth memory slots sharing banks. For this case, only the memory module (single-sided memory bar) can be resolved.
After setting CMOS, why is P4 computer running significantly slow?
Enter the BIOS setup program, "CPU L1 &&l2 Cache" in the BIOS Features Setup option, set it to "enabled", save the CMOS settings to resolve .
