Date: Thu, 13 Apr 1995 05:22:48 +1000 From: Bruce Evans <bde@zeta.org.au> To: ache@freefall.cdrom.com, phk@ref.tfs.com Cc: CVS-commiters@freefall.cdrom.com, ache@astral.msk.su, cvs-sys@freefall.cdrom.com, dufault@hda.com, julian@tfs.com Subject: Re: cvs commit: src/sys/scsi scsi_base.c Message-ID: <199504121922.FAA23975@godzilla.zeta.org.au>
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>The point really is that we print two geometries the same way, >wd0 and sd0, the one for wd0 is useful and true, the one for sd0 >is bogus and not used anywhere, and we don't tell people about >the difference... Actually, the one for wd0 is useful (1) and bogus (2), while the one for sd0 is useless (3) and true (4). Both should be printed. (1) I oversimplified. It isn't useful if it differs from the BIOS geometry. E.g., ESDI drives sometimes say that they have 2 more cylinders than they have, and ESDI and IDE drives may be configured with a different geometry than the one claimed by the drive if the BIOS supports this. (2) I oversimplified. It isn't bogus if it is the same as the physical geometry; there are various levels of bogusness depending on how well translations are hidden from the software. (3) I oversimplified. It's useful if the BIOS geometry is unknown or wrong. E.g., for my 4.3G drive, the BIOS geometry may be is C=1023/H=64/S=32, which loses over 3/4 of the drive, while the geometry printed by the recently restored printf is "(8410200 S), 4076 C 20 H 103 S/T". The problem will be worse for drives larger than 8GB. (4) I oversimplified. The number of sectors/track is usually an average... Bruce
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