Return to BSD News archive
Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!news.rmit.EDU.AU!news.unimelb.EDU.AU!munnari.OZ.AU!spool.mu.edu!howland.reston.ans.net!swrinde!newsfeed.internetmci.com!in2.uu.net!news.vader.org!news.demon.co.uk!dispatch.news.demon.net!demon!awfulhak.demon.co.uk!awfulhak.demon.co.uk!awfulhak.demon.co.uk!not-for-mail From: brian@awfulhak.demon.co.uk (Brian Somers) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: Western Digital 2.5GB IDE HD doesn't work under FreeBSD ! Date: 9 May 1996 15:09:40 +0100 Organization: Coverform Ltd. Lines: 68 Message-ID: <4msub4$21u@anorak.coverform.lan> References: <aak2.830530576@ra.msstate.edu> <4m3dua$3db@uriah.heep.sax.de> <4mdcdu$hqu@uriah.heep.sax.de> X-NNTP-Posting-Host: awfulhak.demon.co.uk X-Newsreader: TIN [version 1.2 PL2] J Wunsch (j@uriah.heep.sax.de) wrote: : brian@awfulhak.demon.co.uk (Brian Somers) writes: : >: What are ``the right parameters'' in your book? : > : >The ones printed on the label on the undercarriage of the disk. : So that is not what you are supposed to tell FreeBSD (unless it's : incidentally the same as your BIOS uses). Btw., unless these ``right : parameters'' look like: : cylinders: 2453 : heads: 15 : sectors per track: 28 ... 45 : youre drive's label is most likely lying. (And if they look like in : my example, how do you enter them into any fdisk editor? <g>) : Your ``right parameters'' are just one possible translation, the one : the vendor recommends (since hopefully it will result in only a : minimal number of blocks being wasted due to transforming the actual : number of blocks into a plain C/H/S scheme). This is what seems to be printed at the bottom of the drive.... from memory, it was something like 4779/31/32. : >One thing I don't understand.... If I say that the drive has 15 sectors, : >37 heads and 102 tracks, and this works controller-wise, does that mean : >that the OS tells the controller the geometry that it wants to use ? : Yes. Traditionally, all BIOSes try to read the very last sector of : the drive during disk initialization, just to see if the parameters : would fit. The disk recomputes the intended geometry out of the C/H/S : values provided in this command, and remembers this one during the : session. It then calculates all C/H/S values presented at the WD-1007 : register interface into logical block numbers, and maps these logical : block numbers to the physical location on the disk (which is not only : recomputing the physical C/H/S values, but also involves bad sector : replacement). : The only requirement is that the C/H/S limits told to the BIOS : multiply up to not more than the total number of blocks on the disk. : There's usually always a small difference between both, and these : blocks are unusable in a system that thinks in C/H/S terms. (For SCSI : disks, FreeBSD can use the entire disk, since it doesn't use the C/H/S : model, and since it's possible to ask the disk about its total number : of blocks available. This will only happen in ``dangerously dedicated'' : mode.) So does FreeBSD use logical block numbers in non-"dangerously dedicated" mode ? Are the C/H/S translations relevent at all or does FreeBSD just look at the logical sector field when fathoming the partition table ? This would make sense to avoid the 10bit cylinder field - and to avoid having to ask the controler to map C/H/S. If this is the case, how come fdisk allows the user to change them ? : -- : 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. ;-) Thanks for your reply(s)..... -- Brian <brian@awfulhak.demon.co.uk> Don't _EVER_ lose your sense of humour....