Date: Mon, 25 Nov 1996 11:05:33 +1100 From: Bruce Evans <bde@zeta.org.au> To: freebsd-current@freebsd.org, j@uriah.heep.sax.de Subject: Re: 2.2-ALPHA install failure Message-ID: <199611250005.LAB08714@godzilla.zeta.org.au>
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>DD mode works with anything of at least 15 spt. I think it works with anything of at least 1 spt (and sufficently many sectors below cylinder 1024 of course). Floppy i/o requests don't cross track boundaries, but the paritition table isn't used by the BIOS for floppies. Hard disk i/o requests do cross track boundaries. A geometry of 15/1/1 should be sufficient for loading the bootstrap :-). >Don't worry. Anything with at least 15 spt will work. IDE drives get >their BIOS geometry from the BIOS setup anyway, not by implying some >semantics to block 0 of the first disk. (This implication as it is >apparently done by some SCSI controllers seems to be a big crock to >me, but oh well, we're in a PeeCee world here.) The loader in the MBR uses the starting C/H/S value to load the secondary bootstrap because it has to use the old BIOS C/H/S interface for portability and converting from the absolute sector number to C/H/S wouldn't fit in the MBR. It takes a lot of code to determine the geometry :-). (Not really, it only takes a single interrupt ask the BIOS for the geometry.) Bruce
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