Dell OptiPlex 990 Service Manual page 79

No timer tick interrupt
Description A chip on the system board might be malfunctioning.
Non-system disk or disk error
Description The floppy disk in drive A does not have a bootable operating
system installed on it. Either replace the floppy disk with one that
has a bootable operating system, or remove the floppy disk from
drive A and restart the computer.
Not a boot diskette
Description The operating system is trying to boot to a floppy disk that does
not have a bootable operating system installed on it. Insert a
bootable floppy disk.
Plug and play configuration error
Description The computer encountered a problem while trying to configure
one or more cards.
Read fault
Description The operating system cannot read from the floppy or hard drive,
the computer could not find a particular sector on the disk, or the
requested sector is defective.
Requested sector not found
Description The operating system cannot read from the floppy or hard drive,
the computer could not find a particular sector on the disk, or the
requested sector is defective.
Reset failed
Description
Sector not found
Description The operating system cannot locate a sector on the floppy or
hard drive.
The disk re-set operation failed.
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