Path: utzoo!mnetor!uunet!tektronix!upvax!stevewa From: stevewa@upvax.UUCP (Steve Ward) Newsgroups: comp.sys.ibm.pc Subject: Re: DOS 3.3 feature vaporware? Message-ID: <425@upvax.UUCP> Date: 2 May 88 05:43:22 GMT References: <4330071@hpindda.HP.COM> Reply-To: stevewa@upvax.UUCP (Steve Ward) Organization: University of Portland, Portland, OR Lines: 35 Summary: Depends on the disk itself... In article <4330071@hpindda.HP.COM> mintz@hpindda.HP.COM (Ken Mintz) writes: >> In the "old days" of the AT, you could FORMAT a 360K disk in a 1.2 MB >> drive with a "FORMAT A: /4".... > > But is that reliable? I've been told that writing to a 360K disk on a > 1.2M drive is not supported. The explanation was as follows: the HD disk > has thinner metallic surfaces, so the 1.2M write heads don't put out as > strong a signal as do the 360K heads. Of course, because the 360K heads > are N times stronger than needed, the 1.2M heads will work X% of the time. > (Anyone have some idea what "X" is?) > >Ken Mintz I've been using 360K disks in my 1.2M drive for some time now. As long as you're only going to be using them in 1.2M drives, they should work OK. Using these disks in a regular 360K drive can be a problem, though. I've found that the best results are obtained if the disk if formatted in a 360K drive. If that's not possible, you can get almost as good reliability by using only blank disks (either new or erased with an electromagnet). You can then format them in the 1.2M drive with the "/4" option (which IS still supported in MS-DOS 3.3) and use them. The problems seem to occur with disks that have been used previously in 360K drives (ie. had data on them), then are re-formatted or DEL *.*'d and use on the 1.2M drive. The reason for this can be traced to the difference in drive head width. The high density drive has a much thinner head than the 360K, so it writes a 360K disk by laying down one thin track in the middle of the wider 360K track. If the disk is then read by a 360K drive, it will "see" both the new track and the outside "strips" of the original wider track. This of course is interpreted as garbage. This indicates to me that there would be no exact "percentage failure" for 360K disks in 1.2M drives. Steve