Power-on self test

ROM ROM stands for read-only memory. It is called read-only because it can t be written to. Once the information has been written to the ROM, it can t be changed. ROM is normally used to store the computer s BIOS, because this information normally does not change. The system ROM in the original IBM PC contained the Power-On Self Test (POST), basic input-output system (BIOS), and cassette BASIC. Later IBM computers and compatibles include everything but the cassette BASIC. The system ROM enables the computer to pull itself up by its bootstraps, or boot (start the operating system). 

It is very easy to tell when a memory error occurs, because a computer malfunctions seriously with bad memory. With a memory error, the computer will do one of two things. If the computer is already running, it will report the error and stop the program. If the error occurs during the POST (power on self-test) memory countup, the computer will not start at all. The reason the computer stops in both cases is that the computer needs reliable memory in order to function. If the computer knows the memory is unreliable, it knows it might write a 1 to memory and read back a 0. And it knows that would be bad. 

The first item we re going to discuss isn t really a hardware problem, but a hardware troubleshooting aid. Every computer has a diagnostic program built into its BIOS called the power on self-test (POST). When you turn on the computer, it executes this set of diagnostics. These tests go by pretty quickly, so we ll detail them here. 

System self-checks and enumerates hardware resources. Each machine has a different startup routine, called the POST (power on self-test), which is executed by the commands written to the motherboard of the computer. Newer Plug-and-Play boards not only check memory and processors, they also poll the systems for other devices and peripherals. 

When a computer is turned on, it first activates the BIOS, which is software that fiicilitates the interactions between the operating system, hardware, and peripherals. The BIOS accomplishes this interaction by first running the power-on self test (POST), which is a set of routines that are always available at a specific... 

A malfunctioning floppy-disk drive can prevent a computer from turning on. If you have a sudden computer failure, try disconnecting the floppy-disk drive and see if the machine will boot into the BIOS. If the machine passes the power-on self-test (POST), then replacing the drive will solve the problem. Also, removing the drive and disabling the drive in the BIOS will immediately return the machine to functionality. 

Switch on the instruments and ensure that all modules power up and perform an electronic self-test. 

The HVPS supplies high-voltage, low-current power to both the charging and transfer corona assemblies in laser and page printers. If it s broken, neither will work properly. If the self-test shows an image on the drum but none on the paper, and the corona assembly is present and not damaged, then the HVPS is at fault. 

Indications on the BPCS workstation or the control panel that all SIS system functions, self-tests, power supplies etc are healthy. Prominent alarms will display if an SIS system fault occurs, messages will indicate follow up actions urgently required. 

For testing under field conditions a new mobile version of introscope has been developed, mounted on a lorry with high cross-country capability and self-contained power supply. 

A constant value of the cell voltage is observed over 6000 hours. Life tests with self-sustaining type cells have shown that open-circuit voltage and power density remain practically constant over a period of more than three years. This is illustrated in Fig. 51. Several cyclings between 1000 °C and room temperature did not affect the performance [107], On the basis of these results, one may conclude that the tubular concept fulfills the life time requirement quite well. 

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