| From: | Andrew Crowe |
| Date: | 4 May 2001 at 19:28:38 |
| Subject: | Re: 40GB HD missing 25% ????? |
Hi Everybody,
>> However, the real size of the disk should be calculated from the
>> physical setup on the disk (cylinders, heads, sectors, etc). It's
>> possible that HDToolbox got those wrong (it gets nearly every other
>> size wrong :). You could try redefining the disk and putting the
>> proper values in, which you'd get on the manufacturers website I
>> would think.
>
> AFAIR HD's do not report the actual physical layout of the drive,
> not any more at least. Cylinders, heads etc are simple chosen such
> that the resulting total number of blocks is the same as that
> available on the drive. Hence I think HDToolbox simply guesses at
> the numbers after it finds out the number of blocks available off
> the drive. I think I read this somewhere in it's docs, but it could
> have been off some lecture notes as well, so dunno.
Nope it doesn't just guess it! :)
HDToolbox reads it from the drive, however IDE drives almost always
report this differently to the actual physical layout of the drives
to better match the IDE optimum and then converts it on the
controller to match the actual drive.
SCSI hard disks however, as SCSI has a much better protocall, usually
report this data correctly as they can read individual heads
independently iirc.
See ya :)
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