IBM 6151 Maintenance And Service Manual page 132

FCx
Unidentified Diskette Drive
The program detected a diskette drive failure, however the
drive type could not be determined. Look at the diskette drive
to determine the drive type; then use the SRA number given
below for that drive type. If needed, see Section 7.
• For the IBM AT High Capacity Diskette Drive, see SRA
number 64x.
If the drive type is not listed above, it is not supported in this
manual.
3-0020-54 Service Manual