Date: Thu, 16 Oct 1997 19:12:19 -0700 (PDT) From: David Filo <filo@yahoo.com> To: mike@smith.net.au Cc: freebsd-hackers@freebsd.org Subject: Re: biosboot/start.S needs fix for Intel AL440LX motherboard Message-ID: <199710170212.TAA22643@ns2.yahoo.com> In-Reply-To: <199710170011.JAA02473@word.smith.net.au> (message from Mike Smith on Fri, 17 Oct 1997 09:41:09 %2B0930)
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> > > The latest BIOS from Intel for their AL440LX board does not pass the > > drive number in %dl as biosboot/start.S assumes (instead %dl is set to > > 0). The end result is that you cannot boot from a harddrive if you're > > not using slices (a "Read error" occurs after the BIOS hands over > > control). Booting from floppy works fine and using slices with bteasy > > works as well. > > Unpleasant. How are you supposed to differentiate between booting from > a harddisk (0x8?) and a floppy (0x0?) ? > you know you're booting from harddisk because that's where the code comes from. the mbr on harddisk assumes it's a harddisk boot. the mbr on floppy assumes it's a floppy boot. > > Forcing %dl to $0x80 (which is what bteasy appears to do) solves the > > problem for me. I assume the real solution is a bit more complex than > > this. I suppose this could be due to some weird BIOS setting, but I > > think I pretty much tried everything. This board will be popular, so > > would be nice to get this fixed. > > Unless Intel are angling for compatability with some other standard, I > think the correct fix will be a BIOS upgrade. If they are, it'd be > handy to know which one, so that we can detect and support it. > > Forcing %dl to 0x80 obviously breaks using the same start.s for both > harddisk and floppy booting. > yep. but doesn't seem like that big a deal to have separate versions. btw, bteasy can deal with %dl not properly set. the first thing it does is check for (%dl == 0x81). if this fails it sets %dl to 0x80. should this solution be used in startup.S as well? in our setup i don't think 0x81 is even possible (how would you get a boot1 from any disk other than scsi id 0?). so doesn't seem too bad to have boot1 on sd0 forced to 0x80. davidhome | help
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