Date: Mon, 20 Nov 2000 20:01:35 +0200 (SAST) From: Robert Nordier <rnordier@nordier.com> To: keithj@sse0691.bri.hp.com (Keith Jones) Cc: stable@FreeBSD.ORG Subject: Re: BootEasy and PC-XT partitions [was Re: Dedicated disks...] Message-ID: <200011201801.UAA28209@siri.nordier.com> In-Reply-To: <20001120174308.A14723@moose.bri.hp.com> from "Keith Jones" at Nov 20, 2000 05:43:08 PM
next in thread | previous in thread | raw e-mail | index | archive | help
Keith Jones wrote: > On a slight side-note to this thread: > > If PC-XT based architectures require a boot sector and partition information > at C0/H0/S0, but reserve the whole of C0/H0, what are the other 62 (or 126?, > for the SCSI oriented) sectors used for? They're "reserved", and on some systems are already used for storing stuff. On other systems, storing anything in this area will cause problems, eg. with virus checking done by the BIOS. In other words, if DD mode is bad, this is potentially worse. > Would it be safe to have a simple bootstrap in C0/H0/S0 to load code from the > rest of C0/H0 and execute it, or are some OSes/applications (e.g. fdisk, > disklabel) likely to hose particular parts of it? (Aside from the partition > table itself, naturally.) No, it wouldn't be safe. Also, it was tried -- still is being tried in -stable -- and doesn't work very reliably for the reasons mentioned above. > Additionally, how many sectors can we actually *guarantee* are there if we > were to include support for legacy IDE disks? (I'm guessing some of the > older ones had less than 63spt, though all mine ended up in the skip long > ago so I can't tell anymore...) We can't guarantee any free sectors are there. Lots of partitions start on the sector immediately following the MBR. Some commercially-supplied FDISKs did this by default for years. It isn't a bad idea, but it isn't a workable solution in itself. It might be OK as an install *option* for a bigger boot manager, but it couldn't be the only option. (And it's really just more sensible to store the entire boot manager in a regular file system, and just store the LBA so the MBR portion can find it.) -- Robert Nordier rnordier@nordier.com rnordier@FreeBSD.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200011201801.UAA28209>