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Path: sserve!newshost.anu.edu.au!munnari.oz.au!news.Hawaii.Edu!ames!elroy.jpl.nasa.gov!swrinde!cs.utexas.edu!natinst.com!hrd769.brooks.af.mil!hrd769.brooks.af.mil!not-for-mail From: burgess@hrd769.brooks.af.mil (Dave Burgess) Newsgroups: comp.os.386bsd.questions Subject: There is a good 'rule of thumb' for disk geometry... Date: 17 Aug 1993 22:09:28 -0500 Organization: Armstrong Laboratory, Brooks AFB, TX Lines: 70 Message-ID: <24s6hm$2on@hrd769.brooks.af.mil> NNTP-Posting-Host: hrd769.brooks.af.mil This thread has been running now for a solid week. If we could only get it into a single rope, we could tie up a battleship... If my understanding of this entire thing is correct, SCSI disks do not care as much about disk geometry as the IDE/ESDI drives. As long as the geometry that is reported by the controller to the boot program agrees with the geometry that is used for the disklabel, there should not be a problem. The caveat is that the controller must come up either in a non-translated mode that *BSD can understand (typ. the physical geometry) or a translated geometry that the controller and disk agree will work (thus faking out *BSD and allowing continuance on its merry way). REGARDLESS: Whatever the disk controller reports as the disk drives geometry on a cold boot without accessing the BIOS is what needs to be used in order to allow *BSD to work with it. I will give you some examples; My Ultrastore 24F will only work in IDE emulation mode. It reports some ridiculous number of sectors and tracks, and a small number of cylinders. Whether these numbers represent the actual disk geometry is moot. The number that is reported on cold boot MUST be used. A no-name IDE controller has a series of jumpers that can be set to pick one of 16 different drive configurations. They are set by approximate size, and the controller and the disk drive coordinate the actual transfers. No matter what the drive's actual physical geometry is, it will appear to the host interface to be n cylinders where each cylinder is 1Meg. Since the controller reports this '1Meg' cylinder size and n cylinders, that is the geometry you should use. The numbers that are reported at cold boot MUST be used. A no-name controller has a single jumper (or CMOS setting, or something) that allows the disk to either be translated or not. The numbers that are reported at cold boot MUST be used. NOTE! The numbers that are reported in the install program may or may not be correct. If the BIOS has gotten its grubby mitts on the controller, it will dutifully report whatever number the BIOS told it to use, instead of the numbers that are reported at cold boot. This is called the endless reboot cycle, or the 'my system boots off the floppy but not off the hard drive' problem. Section 2 of the FAQ, (which, BTW, is available by anonymous FTP from hrd769.brooks.af.mil:~/pub/FAQ) covers this in great grizzly detail. If it still not clear enough, let me know and I will gladly take another run at it. If you do not have access to FTP (I noticed that this particular victim is a UUCP user) I will mail you the silly things. They are deliberately small enough to fit through even the most anal-retentive mail gateway. -- ------ TSgt Dave Burgess NCOIC AL/Management Information Systems Office Brooks AFB, TX -- ------ TSgt Dave Burgess NCOIC AL/Management Information Systems Office Brooks AFB, TX