Date: Thu, 8 Aug 1996 23:03:35 -0700 (PDT) From: Doug White <dwhite@gdi.uoregon.edu> To: "Jeffrey M. Metcalf" <jeffrey_m._metcalf@ccmail.bms.com> Cc: tcg@ime.net, metcalf@imagine.com, questions@freebsd.org Subject: Re: Re[2]: Repair boot sector of IDE hard drive Message-ID: <Pine.BSI.3.94.960808225656.222E-100000@gdi.uoregon.edu> In-Reply-To: <9607088395.AA839519492@ccgate1.bms.com>
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On Thu, 8 Aug 1996, Jeffrey M. Metcalf wrote: > Just as a final note, my collegue and I managed to install FreeBSD > successfully to the entire hard drive and utilized the full 1272 MB of > space. Does that shed any light as to whether it was our BIOS or IDE > interface doing the translation, or is was the Ontrack Disk Manager? FreeBSD doesn't require such niceties as OnTrack to make use of the full disk, so I can't determine if the translation was done by the BIOS or another agent. See below. > We aren't too unhappy at this point that FreeBSD takes up the entire > drive. However, an interesting afterthought. My collegue has two > IDE hard drives > 1GB in size. We only installed to the slave drive > and he reserves the 'Master', C:, drive for DOS and MS Windows. > His C: drive's data is fine, but DOS fdisk reports that it too now > has only a maximum size of 504MB. Fips reports > a corrupted boot sector for the drive entirely filled with FreeBSD, > but doesn't report any such corruption on his C drive. What might > this imply about his setup? However, if you need a translator and don't have it installed, you get this result. DOS communicates with the disk through the BIOS INT 13 calls; it's only as good as the BIOS is. FreeBSD accesses the controller hardware directly and thus bypasses any BIOS limitations during normal operation. THe only place the BIOS comes in is on boot; once the kernel comes up then the wdc driver takes over. Disks >1024 cylinders on non-supporting BIOSs require a translator to fool the BIOS into thinking that the disk is really 1023 cylinders. It does this by mulitplying the number of heads, making the BIOS think the disk has 64 heads (which isn't true, it probably has about 6). Thus: 1024 cylinders x 32 sectors/track (?) x 64 heads = 2,097,152 addressable sectors. (Or something like that -- I am no good at disk math) Doug White | University of Oregon Internet: dwhite@resnet.uoregon.edu | Residence Networking Assistant http://gladstone.uoregon.edu/~dwhite | Computer Science Major
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