From owner-freebsd-hackers Fri Mar 9 2:41:49 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from info.iet.unipi.it (info.iet.unipi.it [131.114.9.184]) by hub.freebsd.org (Postfix) with ESMTP id A9EA637B71A; Fri, 9 Mar 2001 02:41:43 -0800 (PST) (envelope-from luigi@info.iet.unipi.it) Received: (from luigi@localhost) by info.iet.unipi.it (8.9.3/8.9.3) id LAA48528; Fri, 9 Mar 2001 11:42:14 +0100 (CET) (envelope-from luigi) From: Luigi Rizzo Message-Id: <200103091042.LAA48528@info.iet.unipi.it> Subject: howto access an oddly shaped partition on a floppy ? To: hackers@freebsd.org Date: Fri, 9 Mar 2001 11:42:13 +0100 (CET) X-Mailer: ELM [version 2.4ME+ PL61 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Hi, i have the following problem (related to picobsd this is why this msg is Bcc to -small). We can format 1722KB floppies, which is 21 sectors/2heads/82 tracks, but the bios is unable to boot from them -- it will only read the first 18 sectors of each track and in many cases it will be able to read all 82 tracks. So one approach one would use with picobsd floppies could be the following: format the disk with a 1722 format, but then put a regular filesystem only on the "rectangular" area made of 18 sectors/82 tracks. It would be nice to access the rest of the disk (sectors 19-20-21 of each track) as a separate volume. But how do we achieve this ? One way could be to write some userspace program which knows the mapping and reads/writes/seeks for you in the appropriate places. Another one would be to modify the "fd" driver (apparently you need to touch a couple of places in sys/isa/fd.c:fdstate() ) to do the remapping for you, maybe driven by some table or sysctl variable. The latter method would be more flexible as you would be able to use the volume as an ordinary disk. Suggestions ? cheers luigi ----------------------------------+----------------------------------------- Luigi RIZZO, luigi@iet.unipi.it . ACIRI/ICSI (on leave from Univ. di Pisa) http://www.iet.unipi.it/~luigi/ . 1947 Center St, Berkeley CA 94704 Phone (510) 666 2927 . ----------------------------------+----------------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message