Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!aeras!elxsi!len From: len@elxsi.UUCP (Len Mills) Newsgroups: comp.sys.ibm.pc Subject: Re: DOS 3.3 feature vaporware? (really 360k disks) Message-ID: <780@elxsi.UUCP> Date: 2 May 88 18:16:32 GMT References: <4330071@hpindda.HP.COM> Reply-To: len@elxsi.UUCP (Len Mills) Organization: ELXSI Super Computers, San Jose Lines: 37 Keywords: Floppy FORMAT A: /4 Summary: floppy at 1.2 CAN RELIABLY write 360 disks 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 > ... the 1.2M heads will work X% of the time. > (Anyone have some idea what "X" is?) > When the proper procedure is followed "X" is 100. What is this proper procedure, and why does it work? Glad you asked. The data written by a 360k drive is WIDER than than that written by a 1.2m drive. If a disk which was previously written by a 360 is formatted and written by a 1.2, the previous magnetization is not guaranteed to be erased. This remaiming magnetization can cause read errors on either 360s OR 1.2s with slightly different alignment charateristics. The highly reliable procedure is to degauss the 360s before doing the FORMAT A: /4. This can be done in a number of ways, using various equipment. My favorite method is to use a bulk tape eraser built for reel-to-reel tape. Home units can do 10 at a time; computer-room units can do 40 in four stacks of 10 at a time. I position the disks so that the center of rotation is at the center of rotation of the tape reel. This process is reliable and repeatable. >Ken Mintz -- Len Mills ... {uunet,ucbvax!sun,lll-lcc!lll-tis,altos86,bridge2}!elxsi!len