Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!munnari.oz.au!metro!ipso!runxtsa!brucee From: brucee@runxtsa.runx.oz.au (Bruce Evans) Newsgroups: comp.os.minix Subject: Re: PC Minix and 1.44MB floppies Message-ID: <2154@runxtsa.runx.oz.au> Date: 10 Aug 90 21:18:46 GMT References: <3851@crash.cts.com> Organization: RUNX Unix Timeshare. Sydney, Australia. Lines: 37 In article <3851@crash.cts.com> cwr@pnet01.cts.com (Will Rose) writes: >one 360KB and one 1.44MB floppy. MSDOS 3.3 diskcopy works for 360KB disks, >but I found that 'diskcopy b: b:' attempted to reformat the target disk to >15 sectors/track, ie. the spt for a 1.2 MB device. This despite the fact It only works for DOS disks. It reads the a parameter block on the first sector, and gets confused if there is Minix `garbage' there. Even 360K disks may be treated as single-sided. > dd if=file of=/dev/fd1 bs=1k count=1440 takes 7 min. > dd if=/dev/fd1 of=file count=2880 takes 6 min. This is normal on a 5MHz XT (except bs=1k ought to be the fastest). The floppy driver is too slow. It spends several msec processing in between blocks when it can only aford 1msec. This results in 1 block of i/o per revolution. It takes about a 10MHz AT to keep up (at least for a 1200K disk), giving an i/o time of about 40 sec for copying an 80-track floppy to a file on a hard disk. For a 1440K disk you need a couple more MHz. >Are these times typical, and is there any input buffering or whatever that >could speed things up? I'm using a 'safe' filesystem, with blocks written There's already considerable buffering in FS. Otherwise the time for 512b blocks would be twice as long as for 1k and the time for 1k might be 9 times as long as for 9k. (The best block size is the smallest multiple of the head sizethat gives a whole number of blocks, i.e. 1 * 9k here, 2 * 4.5k, 2 * 7.5k, etc.) Your times are about 9 times as slow as they would be if the floppy driver was taking advantage of the buffering. I wondered if anyone used the `safe' filesytem update. It's not so safe for the drive (more wear) or the computer (user may get tired of waiting and get something faster :-). Actually, it hardly matters here because no inodes are being written to the floppy. -- Bruce Evans Internet: brucee@runxtsa.runx.oz.au UUCP: uunet!runxtsa.runx.oz.au!brucee (My other address (evans@ditsyda.oz.au) no longer works)