Date: Tue, 2 Apr 1996 14:36:08 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: j@uriah.heep.sax.de (J Wunsch) Cc: freebsd-hackers@FreeBSD.org Subject: Re: fdisk and partition info Message-ID: <199604022136.OAA17244@phaeton.artisoft.com> In-Reply-To: <199604021827.UAA10603@uriah.heep.sax.de> from "J Wunsch" at Apr 2, 96 08:27:43 pm
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> > > However, these numbers are `real', but inaccessible. The SCSI > > > protocol doesn't let you enter any of these numbers in a SCSI command. > > > That's why you cannot turn off the ``translation''. > > > > Again, the translation I refer to is that which is done by the BIOS. > > Again, all SCSI BIOSes must translate, since SCSI is LBA by > definition, while the int 0x13 interface is C/H/S by definition. > FreeBSD does never translate, since it uses LBA as its API to the > driver. Again, the physical laws of the universe do not require that it be impossible to obtain the C/H/S geometry from protected mode. This is prevented by SCSI controller manufacturers, not God. As long as the translation is consistent (which it is for some controllers), the translation can be an attribute of the controller, and the S multiplier can be determined by asking the drive how many different seek motor positions it has and how man heads it has, and dividing the total number of sectors by these values and throwing away the remainder to get the DOS geometry. A correct controller will provide the same lies to the protected mode question as it provides to the BIOS call question. This is the difference between controller hardware and controller software translation. Disk level translation is not detectable by software. The other kind is (FreeBSD is software, and it detects it by screwing up). It is only the piece-of-crap Adaptec controllers with "advanced" setups that vary the geometry undetectably from the controller probe. Like my old EISA 1742, which I can't ask which mode it is in without being able to read (and interpret) the EISA slot configuration information. Most SCSI controllers fit the geometry assumptions made by the slice code. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.
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