Hardware Reference
In-Depth Information
Note
Some IBM computers since 1987 display a strange character graphic depicting the front of a
floppy drive, a 3 1/2-inch disk, and arrows prompting you to insert a disk in the drive and
press the F1 key to proceed.
Older Compaq BIOS:
Non-System disk or disk error
replace and strike any key when ready
Although the messages vary from BIOS to BIOS, the cause for each relates to specific bytes in
the MBR, which is the first sector of a hard disk at the physical location cylinder 0, head 0,
sector 1.
The problem involves a disk that either has never been partitioned or has had the Master Boot
Sector corrupted. During the boot process, the BIOS checks the last two bytes in the MBR (first
sector of the drive) for a signature value of 55AAh. If the last two bytes are not 55AAh, an
Interrupt 18h is invoked, which calls the subroutine that displays one of the error messages just
shown, which basically instructs the user to insert a bootable floppy to proceed.
The MBR (including the signature bytes) is written to the hard disk by the FDISK, Disk
Management, or DISKPART programs. Immediately after a hard disk is low-level formatted,
all the sectors are initialized with a pattern of bytes, and the first sector does not contain the
55AAh signature. In other words, these ROM error messages are exactly what you see if you
attempt to boot from a hard disk that has been freshly low-level formatted but has not yet been
partitioned or if the MBR has been corrupted such that the signature bytes were overwritten.
21.
The MBR searches its built-in partition table entries for a boot indicator byte marking an
active partition entry.
22.
If none of the partitions are marked active (bootable), the BIOS invokes software interrupt 18h,
which displays an error message (refer to step 20).
23.
If any boot indicator byte in the MBR partition table is invalid, or if more than one indicates an
active partition, the following message is displayed and the system stops:
Invalid partition table
24.
If an active partition is found in the MBR, the partition boot record from the active partition is
loaded and tested.
25.
If the partition boot record can't be read successfully from the active partition within five
retries because of read errors, the following message is displayed and the system stops:
Error loading operating system
26.
The hard disk's partition boot record is tested for a signature. If it does not contain a valid
signature of 55AAh as the last two bytes in the sector, the following message is displayed and
the system stops:
Missing operating system
