Date: Tue, 21 May 1996 14:20:05 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: grog@lemis.de (Greg Lehey) Cc: terry@lambert.org, dutchman@spase.nl, freebsd-hackers@FreeBSD.org Subject: Re: Glitch in install procedure. Message-ID: <199605212120.OAA02080@phaeton.artisoft.com> In-Reply-To: <199605211017.MAA23956@allegro.lemis.de> from "Greg Lehey" at May 21, 96 12:17:40 pm
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> >> I just installed FreeBSD as a secondary OS on a machine. I dumped it into the > >> upper 300 Mb of a 810 Mb disk. Funny thing is that neither the installation > >> procedure, nor booteasy issued a warning that it would not be possible to > >> actually boot from the partition, as it is beyond the reach of the BIOS. > > > > That's because it couldn't ask BIOS to tell it what was good. > > No, but it could issue a warning. Kees didn't ask for it to refuse to > install. Question: in order to warn you if absolute sector X is past cylinder 1024, it needs to: X%(H*S) Remainder is H/S value X/(H*S) Integer value is cylinder So if it doesn't know the C/H/S geometry (sure, we can guess that the BIOS geometry is the Adpatec geometry, but we need to be prepared when it isn't), how can we say "cylinder past 1024"? BSD drivers operate on absolute sectors (and *only* on absolute sectors). BIOS drivers operate on C/H/S values, thet the INT 13 interface translates into controller C/H/S values -- or absolute sectors. The controller that uses controller C/H/S values translates them into -- absolute sectors. The only way to know the BIOS C/H/S values for sure is to ask the BIOS. 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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