Xref: utzoo comp.sys.ibm.pc.hardware:7447 comp.multimedia:315 comp.misc:12039 Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!elroy.jpl.nasa.gov!decwrl!deccrl!bloom-beacon!eru!hagbard!sunic!news.funet.fi!cc.tut.fi!public From: public@cc.tut.fi (PD Software Group) Newsgroups: comp.sys.ibm.pc.hardware,comp.multimedia,comp.misc Subject: Re: Diffs between DD & HD disks Message-ID: <1991Apr9.191024.7048@cc.tut.fi> Date: 9 Apr 91 19:10:24 GMT References: <1991Apr9.042503.18670@bilver.uucp> <1991Apr9.065832.16253@cs.ucla.edu> <1991Apr9.141703.5134@cs.dal.ca> Organization: Tampere University of Technology, Finland Lines: 42 In article <1991Apr9.141703.5134@cs.dal.ca> paixao@ug.cs.dal.ca (Nuno M. Paixao) writes: >I was using a machine with a high density 3.5" floppy in it, and wasn't aware >that it was high density. Whenever I formatted a disk ( a DS/DD) I simply >typed FORMAT. The machine then formatted them to High density. There are some 3.5" drives which can't determine if the disk is DD or HD. Such drives are used at least on IBM PS -computers. > >While using that machine, I could store 1.4MB of information on that disk, >bu then I tried to take one of those disks to another machine. Neither >a low density nor a high density floppy could read my disks ( and there were >about 12 of them.) Since I had lost access to the orginal machine, >I lost over 10 MB of stuff. I wasn't impressed. :-( That was because the drive with you formatted the disks couldn't determine if the disk is DD. The other drive noticed that the disk you had formatted with previous drive does not have the HD hole. So it thought that disk is DD and failed to read it since the sectors on DD and HD disks are different size (both DD and HD can contain 512 bytes, but on DD there are 9 sectors per track when HD has 18 sectors per track). Since you dont have access to that original machine, you could try this (I mean if you still have those disks): Make a hole to DD disk at the same location than on the HD disk's HD hole is and try then read the disk on the HD drive. It should be usable again. >The point of the story is: > If your disk says DS/DD format it to 720K. > If it says DS/HD then format it to 1.44MB. I disagree with this. Whatever the manufacturers say about the differences with the media of DD and HD disks (I admit that most likely there is some differences between DD and HD disks), it is quite reliable to use 'hand-made-HDs'. A friend of mine has used such disks for YEARS without problems - nowadays he has 900-1000 hand-made (and even nameless) DD-HDs -- Tapio Keih{nen | "Whenever you dream Mesihein{nkatu 2 B 6 | you're holding the key, 33340 Tampere, Finland | it opens the door public@cc.tut.fi | to let you be free" - RJD '85