Date: Fri, 14 Sep 2001 17:48:59 +0200 From: Erik Trulsson <ertr1013@student.uu.se> To: Peter Pentchev <roam@ringlet.net> Cc: freebsd-hackers@FreeBSD.org Subject: Re: Does boot1 still have a > 1023 cyl limit? Message-ID: <20010914174859.A53427@student.uu.se> In-Reply-To: <20010914180622.A512@ringworld.oblivion.bg> References: <20010914180622.A512@ringworld.oblivion.bg>
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On Fri, Sep 14, 2001 at 06:06:22PM +0300, Peter Pentchev wrote: > Hi, > > A quote from the end of the boot_i386.8 manual page.. > > IMPORTANT NOTE: Because of limitations imposed by the conventional disk > interface provided by the BIOS, all boot-related files and structures > (including the kernel) that need to be accessed during the boot phase > must reside on the disk at or below cylinder 1023 (as the BIOS under- > stands the geometry). When a ``Disk error 0x1'' is reported by the sec- > ond-stage bootstrap, it generally means that this requirement has not > been adhered to. > > Just today I had a friend ask me if this is still true; I checked CVS > history and found out that this comment was added by rnordier more than > two years ago. Is this still true? I think it depends on the BIOS. The first stages of the bootstrap sequence use the BIOS to read from the disk. The original BIOS calls for reading/writing the disk does not support cylinder numbers larger than 1023. On later BIOSes extensions have been added to allow access to cylinders above 1023. Nowadays the FreeBSD bootstrap is able to use these BIOS extensions. This capability was added about a year ago. (From reading the CVS logs it seems 4.1 was the first release to support this.) But to use this requires that the BIOS support these extensions. All modern machines do AFAIK but many older machines don't. To sum it up: If you have a modern BIOS you can boot from anywhere on the disk (assuming a recent version of FreeBSD) but older BIOSes do not support this. Anybody who knows when BIOSes in general were extended to support >1024 cylinders? My *guess* would be 1997 or thereabout. -- <Insert your favourite quote here.> Erik Trulsson ertr1013@student.uu.se To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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