Hard disk repair soft errors

In fact, a large number of hard drive failures are soft failures, such failures also accounted for a large proportion of computer failures, and these failures can be users themselves, and the following, we mainly target a number of soft errors frequently occur phenomenon, about the maintenance of their skills.

First, the maintenance of the hard disk bootstrap failure

Practical application, the hard disk bootstrap failure is very common, hard disk bootstrap failure generally have the following symptoms:
Show "BASIC ... OK", enter the ROM BASIC.
Display "Invalid partition Table", is invalid partition table.
Display "Error loading operating system", read boot record failure and enter an infinite loop.
Shows "Operating system missing operating system" is not the operating system.
Show "NOn-System disk or disk error"
"Replace and strike any key when ready", read boot error.
Shows "Disk boot failure", Disk Boot failure into an infinite loop.
Show "Bad or missing command interpreter", COM-MAND.COM no or destroyed.

1. With the hard disk to start the boot process module and its boot






The hard disk from the hard disk of boot ROM BIOS, the hard disk master boot record, DOS boot record and system files completed. ROM BIOS, a total of 8K bytes, providing self-test, bootstrap capability and the establishment of the hard disk I / O and a series of operations, contained in the hard disk of boot module is the interrupt routine INT19H; hard disk master boot record in the 0 column 0 a sector (physical sector), before the row of logic 0 sector, including the hard disk boot loaders and partition information table, sector of the last two bytes "55A", is a hidden sector, with the DEBUG command or DOS function call INT 21H and were unable to read and write, usually provided by the ROM BIOS interrupt service routine INT13H hard to read and write an absolute, DOS Boot Record partition the hard disk 0 column 0 2 sector (physical sector, the entire hard drive was placed under DOS partition), that is the logical sector 0 to end the logo is also a "55AA".

The system power-up, the computer's execution flow is as follows:

CPU into the reset state of well-Qiang Chi CS: IP = FFF: 0000H, the address obtained from the first instruction (jump instructions).
The system transferred to the ROM BIOS program areas, the implementation of self-test procedure, if the self-test is successful, directing the INT19H systematic guidance, or reveal the error message and enter an infinite loop.
INT19H first tries to reset the floppy disk system, if successful, then read the first one of the DOS floppy boot record to the starting address 0000:7 C00H memory cell implementation, and then enter the DOS, or reset the hard disk system.
The success of the reading of the hard disk master boot record to the starting address 0000:7 C00H memory unit, and implement the master boot process, if the reset fails, read the master boot record error, or hard physical first one the last two bytes are not "55AA" , have shown that:
"BASIC ... OK" into the ROM BASIC.
The hard disk master boot program main function is to identify the current active partition, that is, view the partition information in the table 4 partition boot flag, when the DOS partition boot logo 80H, while the other partition 00H, will read the memory DOS Boot Record 0000:7 C00H Department.
If the four partition did not boot logo (80H), then the hair INT18 instruction into ROM BASIC;
If the boot flag (80H) more than one or a partition for the boot flag is neither 80H, then the non-00H, is displayed "Invalid partition table" and enter an infinite loop.
Find the active partition, the master boot record program attempts to read the memory, DOS Boot Record 0000:7 C00H Department, if the read fails, it displays: "Error LoadongSystem" and enter an infinite loop.
Read the success of the DOS boot sector checks whether the last two bytes of "55AA", the correct implementation of the jump 0000:7 C00H just read into the DOS boot process, if not, then the Show:
"Missing operating system" and enter an infinite loop.
Guide the process to AH = OINT13H command reset disk system, if the failure is displayed:
"Non-system disk or disk error"
"Replace and strike any key when ready"
Wait for keyboard input in order to shift INT19H re-boot.
If successful, then the calculation of the file directory area and the file data area start-bit sector numbers, and read the root directory of the first one to 0050:007 H office, if the read fails, an error message is displayed on.
If correct then the reading of "IBMBIO.COM" file into memory. If the reading error is displayed:

"Disk boot failure" into an infinite loop.

If the reading success, by IBMBIO.COM, IBMDOS.COM and COMMAND.COM three DOS system files, continue with the installation, during which, if can not find COMMAND.COM or the file is corrupt, then the show "Bod or missing command interpreter ".
Otherwise, a normal guide, until the system prompt, waiting for users to type a DOS command.
At this point, the system into DOS working condition.

2. Bootstrapping failed hard disk repair

If a normal hard disk drives, hard disk bootstrap failure and hard disk master boot module, DOS boot modules and system files are closely linked. For example, boot into ROM BASIC is likely to damage the hard disk master boot record; and failure to guide reveals the error message, then with the partition information table, DOS boot record and system files on damaged or missing. For a different error message, we should find out the crux of the problem and then take corresponding repair method is presented as follows:
(1) repair the hard disk master boot record
Using the hard disk master boot module versatility, from another of the normal and hard disk partitions on the same computer access to the module, and then write back to the hard disk failure, this method is simple and quick, even for the master boot block structure, a very shallow understanding of , did not find it difficult to operate, the steps are as follows:
① to start a normal computer, and drive home an A blank, formatted disk, type the following statement sequence:
C> DEBUG
-A 100

? ? ? ? : 0100 MOV AX, 0201; reading a sector
? ? ? ? : 0103 MOV BX, 1000; set buffer CS: 1000

? ? ? ? : 0106 MOV CX, 0001; reading 0 Column No. 1
? ? ? ? : 0109 MOV DX, 0080; the hard disk head, No. 0
? ? ? ? : 010C INT 13; disk I / O interrupts

? ? ? ? : 010E INT 20; program termination.
? ? ? ? : 0110

-G = 100

-W 1000 0 50 1

At this point, has been good and hard disk master boot block and write the logic in the floppy disk sector 50H.
② The DOS floppy disk boot failure of the computer, after entering DEBUG into the floppy disk drive A, type the statement in the DEBUG state sequence:

-L 1000 0 501

-A 100

? ? ? ? : 0100 MOV AX, 0301: to write a sector
? ? ? ? : 0103 MOV BX, 1000

? ? ? ? : 0106 MOV DX, 0001

? ? ? ? : 0109 MOV DX, 0080

? ? ? ? : 010C INT 13

? ? ? ? : 010E INT 20

? ? ? ? : 0110

-G = 100

At this point, the hard disk master boot record repair is completed.