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Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!news.rmit.EDU.AU!news.unimelb.EDU.AU!cs.mu.OZ.AU!munnari.OZ.AU!news.hawaii.edu!news.uoregon.edu!news-res.gsl.net!news.gsl.net!news.sprintlink.net!news-dc-5.sprintlink.net!news.sprintlink.net!news-dc-2.sprintlink.net!news.mathworks.com!news.kei.com!newsfeed.internetmci.com!in1.uu.net!fu-berlin.de!news.belwue.de!news.uni-stuttgart.de!uniol!uni-erlangen.de!news.tu-chemnitz.de!irz401!orion.sax.de!uriah.heep!news From: j@uriah.heep.sax.de (J Wunsch) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: IDE Hard Disk questions Date: 22 Jun 1996 11:50:24 GMT Organization: Private BSD site, Dresden Lines: 35 Message-ID: <4qgmm0$q31@uriah.heep.sax.de> References: <4pp2no$334@news.ida.org> <4pv1c3$84e@uriah.heep.sax.de> <DtB9oz.25L@info.elvisti.kiev.ua> Reply-To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch) NNTP-Posting-Host: localhost.heep.sax.de Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Newsreader: knews 0.9.6 X-Phone: +49-351-2012 669 X-PGP-Fingerprint: DC 47 E6 E4 FF A6 E9 8F 93 21 E0 7D F9 12 D6 4E stesin@elvisti.kiev.ua (Andrew V. Stesin) wrote: > : If the drive is FreeBSD and FreeBSD only, you can select any geometry > : you want when using the ``dangerously dedicated'' mode. > Is this also true for IDE drives? I mean -- will just > plain motherboard BIOS, not the SCSI HBA's one, live fine > with this? Of course, as long as your BIOS thinks that your drive has at least 15 sectors (the size of the primary bootstrap) per track. I don't know of any BIOS that fails this assumption (unless purposely mis-dictated via the custom disk type of your setup). Remember that the BIOS is used only, really *only*, to load the kernel into memory. FreeBSD's limits for a wd-style drive are c=65536, h=16, s=255 (127.5 GB). Since FreeBSD must use the same h and s figures as the BIOS, the above figures shrink for disks that must be shared with the BIOS (e.g. boot disks) to c=65536, h=16, s=63 (31.5 GB), due to the int 0x13 limitation to only 6 bit sector numbers. The other values are mandated by the register interface of the hardware, in particular there are only 4 bits to address the head number. As you can see, the limits (31.5 GB or 127.5 GB) are quite a bit larger than for messy DOS. That's what you're getting for designing (and using) a crippled and unextensible BIOS interface... :-) -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)