Re: Origin of hard drive parameters
- From: Chuck Swiger <cswiger@xxxxxxx>
- Date: Wed, 6 Sep 2006 11:55:17 -0700
On Sep 6, 2006, at 11:40 AM, Hilt, Ian wrote:
Basically, I want to know where the BIOS gets the hard drive parameters
when the Drive Type is set to "AUTO" in the BIOS configuration. The best
I've been able to come up with from the internet is an "IDENTIFY"
command that purportedly
(<http://www.linux.com/howtos/Large-Disk-HOWTO-10.shtml>) gets its
information from the "IDE controller". This does not answer my question
completely. Are the parameters returned by the controller hard coded
into a chip on the board or are they on the platters of the hard drive,
or neither?
"Neither" is probably the best answer.
The hard disk has an on-board controller which answers the ATA "IDENTIFY DEVICE" command with the hard drive parameters used by the BIOS, assuming that the BIOS is operating in the legacy C/H/S mode rather than the newer LBA mode which uses absolute block numbers. Note that the answer the drive controller gives will normally be a fabricated geometry which does not have anything to do with the actual geometry of the physical device, in part because drives nowadays keep a variable number of sectors per track rather than using a CAV layout.
--
-Chuck
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