Date: Sun, 8 Jun 1997 15:25:06 -0400 (EDT) From: Chuck Robey <chuckr@glue.umd.edu> To: =?ISO-8859-1?Q?Ricardo_N=FA=F1ez?= <rinunez@telcel.net.ve> Cc: FreeBSD Hackers <freebsd-hackers@FreeBSD.ORG> Subject: Re: 504 MB Limit Message-ID: <Pine.BSF.3.96.970608151806.323S-100000@Journey2.mat.net> In-Reply-To: <19970608101105.AAA4908@telcel.telcel.net.ve>
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On Sun, 8 Jun 1997, Ricardo Núñez wrote: > Dear Gentlemen, > > I have the following things: > > - FreeBSD 2.2.1 CD-ROMs > - "The Complete FreeBSD" book from Greg Lehey. > - A PC Clone with a Triton Motherboard, 24 MB RAM and... > - An IDE (EIDE?) disk which has 1280 MB capacity (620 cylinders, 64 heads, > 63 sectors) > - All the hard disk has a working Windows 95 environment in one partition. > > I´d like to avoid Greg Lehey´s advice which said (page 30) that I have to > put my root FreeBSD slice before the first 504 MB. My BIOS DOES support > that disk with its 1280 MB. I don´t have to "run" any special booting > software. I´d like to keep a whole C: FAT Win95 partition (with no Extended > DOS partition). So.... > > Can I split my disk in just two slices: an old DOS partition just with less > disk space, and all the rest (let´s say around 300 Mb) to FreeBSD slices > without having to take care of 504 MB problem? > > Thank you very much in advance, The trouble is not in the geometry directly, it's in how the bios keeps track of cylinders. See, the bios is what produces the vector that finds the FreeBSD partition. Once the FreeBSD partition has been found by the bios, FreeBSD software takes over. The trouble is, the bios uses a 10 bit number to keep track of the cylinder, so it can only produce vectors between 0 and 1023. Back when I used IDE drives, my drive had a hardware pin that let it cheat and double the number of sectors per track, and artifically then halve the number of cylinders. You had to have formatted the drive that way, but it let the bios see the whole drive. If you don't have something like that, then you are indeed limited. Also, don't rely on any software disk manager to do it, because booting occurs before such software has been loaded. So, even tho your disk parameters may be correctly listed in your bios, you have that limitation: the boot sector of a bootable partition must begin in cylinders 0-1023. ----------------------------+----------------------------------------------- Chuck Robey | Interests include any kind of voice or data chuckr@eng.umd.edu | communications topic, C programming, and Unix. 213 Lakeside Drive Apt T-1 | Greenbelt, MD 20770 | I run Journey2 and picnic, both FreeBSD (301) 220-2114 | version 3.0 current -- and great FUN! ----------------------------+-----------------------------------------------
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