Onboard Drive Diagnostics; Ecc Performance Tests - Seagate ST3660A - Medalist 545 MB Hard Drive Product Manual

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Disc errors encountered during Write Multiple commands are posted
after the attempted disc write of the block or partial block transferred. The
Write command ends with the sector in error, even if it was in the middle
of a block. Subsequent blocks are not transferred in the event of an error.
Interrupts are generated when DRQ is set to 1 at the beginning of each
block or partial block.
The contents of the Command Block registers are undefined when they
follow the transfer of a data block that had a sector in error. The host
should retry the transfer as individual requests to obtain valid error
information.

3.4 Onboard drive diagnostics

During startup, the drive executes a series of diagnostic tests. If the
diagnostic tests detect an error, the drive LED indicates the nature of the
error by emitting a flash code. A subset of the error flash codes is
contained in the following table.
Number of
flashes Error code description
Irregular flashes Microprocessor error
2 ROM checksum error
3 External RAM error
4 I/O chip error
5 Buffer RAM error

3.5 ECC performance tests

The drive does not report ECC errors when it performs on-the-fly error
correction. This allows the drive to correct the data without sacrificing
performance.
Some older drive diagnostic utilities test the drive's ability to apply ECC
by creating small data errors and then checking to see if these errors are
reported. If you run one of these tests on a drive that is functioning
properly, the test may report that the drive is failing to detect ECC errors.
However, this does not mean that the drive is malfunctioning.
Medalist XE Family Product Manual, Rev. B