Path: utzoo!utgpu!watserv1!watmath!att!dptg!pegasus!psrc From: psrc@pegasus.ATT.COM (Paul S. R. Chisholm) Newsgroups: comp.sys.ibm.pc Subject: Re: Formatting 1.2 Meg disks to 360K question Summary: at least, not on a 360K drive Message-ID: <4407@pegasus.ATT.COM> Date: 18 Jan 90 17:53:05 GMT References: <3226@ucrmath.UCR.EDU> <7715@nigel.udel.EDU> Organization: AT&T Bell Laboratories Lines: 60 In article <25AD7F7A.26599@maccs.dcss.mcmaster.ca> cs4g6ag@maccs.dcss.mcmaster.ca (Stephen M. Dunn) writes: > If the problem was that 360K drive heads didn't generate strong > enough magnetic fields, then I should be able to format 1.2M > floppies at 360K in my 1.2M drive. Well, it doesn't work any better > in that drive than it does in my 360K drive. In article , jacobs@cs.utah.edu (Steven R. Jacobs) writes: > This would imply that 1.2M drives cannot write data on 360K disks, but > people do this all the time. What he (Steven) said. (BTW, I've tried variations on this, such as trying to format a DSHD floppy in a DSQD (quad density) drive, or trying to format a 3.5" DSHD floppy in a DSDD drive. It didn't work; the coercivity of the higher density disk was more than the write head in the lower density drive could handle.) > I've had no problem reading or writing > 360K disks in 1.2M drives (this is not a good idea, however, since many > 360K drives will have trouble reading data written by a 1.2M drive even > if the floppy is formatted at 360K originally). Again, ditto. Some 1.2M drives (e.g., Qume, from earlier reports on the net) are better than others at this. The most commonly successful effort is to format on a 360K drive, write once on a 1.2M drive, and never write on the disk again with either drive. The alternative I've seen on the net is to format *and* write with the 1.2M drive. (Formatting and writing with a 360K drive will work, of course; the trick is what to do if you don't have a 360K drive handy.) > The problem with formatting 1.2M floppies at 360K is the difference > in the width of the recording heads. The recording heads for a 1.2M > floppy are about 1/3 the width of the recording head in a 1.2M floppy. > The 360K drives sometimes have trouble reading the narrow data path > created by the 1.2M recording heads. Yup. > Now I'm sure you will point out that the 1.44M microfloppy drives will > format/read/write data at 720K. The reason that this works is that the > data is _exactly_ twice as dense, so that the 1.44M drive can write the > data on two neighboring tracks to make it look like 720K data. Nope; a 1.44M drive has twice the number of sectors per track, but the same number of tracks (of the same width and density) as the 720K. > This is > not possible with the 1.2M drive, since 1.2M is not an integer multiple > of 360K (there are probably other complications as well). A 1.2M disk has exactly twice as many sectors per track, and twice as many (narrower) tracks, as a 360K disk. > Steve Jacobs ({bellcore,hplabs,uunet}!utah-cs!jacobs, jacobs@cs.utah.edu) Paul S. R. Chisholm, AT&T Bell Laboratories att!pegasus!psrc, psrc@pegasus.att.com, AT&T Mail !psrchisholm I'm not speaking for the company, I'm just speaking my mind.