Richard B. Johnson wrote:
Then I suggest you never use such a drive. Anything that does this,
will end up replacing a good track with garbage. Unless a disk drive
has a built-in power source such as super-capacitors or batteries, what
happens during a power-failure is that all electronics stops and
the discs start coasting. Eventually the heads will crash onto
If the power to the drive is truly just cut, then this is basically what
will happen. However, I have heard, for what it's worth, that in many
cases if you pull the AC power from a typical PC, the Power Good signal
from the PSU will be de-asserted, which triggers the Reset line on all
the buses, which triggers the ATA reset line, which triggers the drive
to finish writing out the sector it is doing. There is likely enough
capacitance in the power supply to do that before the voltage drops off.
the platter. Older discs had a magnetically released latch which would
send the heads to an inside landing zone. Nobody bothers anymore.
Sure they do. All current or remotely recent drives (to my knowledge,
anyway) will park the heads properly at the landing zone on power-off.
If the drive is told to power off cleanly, this works as expected, and
if the power is simply cut, the remaining energy in the spinning
platters is used like a generator to provide power to move the head
actuator to the park positon.
--
Robert Hancock Saskatoon, SK, Canada
To email, remove "nospam" from [email protected]
Home Page: http://www.roberthancock.com/
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