AT&T 6300 Service Manual page 256

DIAGNOSTICS
Memory Disk Transfer is also performed during this phase.
This particular routine creates a file on drive A. Because of this,
a formatted nonwrite-protected disk must be present in
drive A. This may be a nonwrite-protected copy of the
system test or the scratch diskette used for the floppy tests.
If this test is used with a write-protected diskette in drive A,
either of the following messages appear.
[ WRITE PROTECT ERROR WRITING DRIVE A:
]
[ABORT, RETRY, IGNORE?
]
Note: On ABORT, you will return to the operating
system.
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