jim@jagmac2.gsfc.nasa.gov (Jim Jagielski) (07/05/90)
As far as I know, there are two ways to get the geometry of your disk drive:
use SCSI Evaluator or use SilverLining... However, these applications
return different values for the number of cylinders for all my disks!
For example, for my Quantum 80 (the 3 1/2 version), SCSI Eval returns 834
cylinders, whereas SilverLining returns 837... which is correct??
(SCSI Eval is version 1.00 and 1.03, same answer; SL is 5.24/09)
Any body have any ideas/answers??
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#include <std/disclaimer.h>
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Jim Jagielski NASA/GSFC, Code 711.1
jim@jagmac2.gsfc.nasa.gov Greenbelt, MD 20771
"Kilimanjaro is a pretty tricky climb. Most of it's up, until you reach
the very, very top, and then it tends to slope away rather sharply."ts@cup.portal.com (Tim W Smith) (07/07/90)
< For example, for my Quantum 80 (the 3 1/2 version), SCSI Eval returns 834 < cylinders, whereas SilverLining returns 837... which is correct?? < (SCSI Eval is version 1.00 and 1.03, same answer; SL is 5.24/09) According to the manual for these drives, they have 834 cylinders. This is also what I get when I issue a MODE SENSE command to read page 4, which contains this information. There are 6 heads. There are 0 sectors/track, according to the drive, which means that the number of sectors/track is variable. Cylinders 0 to 590 have 35 sectors/track, and 591 to 833 have 28. (Note: if you calculate the drive capacity based on the drive geometry, you will get a number larger than the capacity reported by a READ CAPACITY command. This is because some of the disk is used for defect management.) A Macintosh does not care about drive geometry. Other computers do. For example, DOS systems like to think in terms of cylinders and heads and sectors. When one is supporting a SCSI drive on such systems, one has to make up a geometry for the drive. A typical way is to get the geometry information from the drive, and then cut down the number of cylinders until the capacity calculated from the geometry is not greater than the capacity reported by READ CAPACITY. These geometry values are then reported to DOS. On the other hand, there is no really good reason to report to DOS a geometry that has any relationship to the real geometry. Indeed, when you have a drive with a variable number of sectors/track, you've got to make something up. The above explains why the same SCSI drive might show up with different drive geometry parameters under different programs on DOS, but I have no idea why Macintosh programs would do this. Tim Smith