davidr@hplsla.HP.COM ( David Reed) (12/02/86)
By way of comment from my experience: I have found with the great variety and
numbers of computers I use around here that:
a 360K disc formatted in a 1.2M drive (with the /4 option to format as
a 360K disc, of course) canNOT be read in about 1/3 of the 360K
drives when a 1.2M drive also writes the data to the disc, but
a 360K disc formatted in a 360K drive and written to by a 1.2M drive
can NEARLY always be read in a 360K drive.
Most of our new machines have ONLY 1.2M drives for floppies, but we have a
couple of machines with a 360K drive installed as a second floppy drive simply
for the above purpose, to format a 360K disc so that it will more likely be
readable by an older 360K drive (even if it might have data written on it by
the 1.2M drives).
-David M. Reed hplsla!davidrmjg@ecsvax.UUCP (Michael Gingell) (12/08/86)
In article <2690002@hplsla.HP.COM>, davidr@hplsla.HP.COM ( David Reed) writes: > By way of comment from my experience: I have found with the great variety and > numbers of computers I use around here that: > a 360K disc formatted in a 1.2M drive (with the /4 option to format as > a 360K disc, of course) canNOT be read in about 1/3 of the 360K > drives when a 1.2M drive also writes the data to the disc, but > a 360K disc formatted in a 360K drive and written to by a 1.2M drive > can NEARLY always be read in a 360K drive. > I would disagree with the above entirely. The above rules are either accidentally reversed or a recipe for disaster. Disks made on 360k drives should NEVER be written to with a 1.2 Meg drive if you want to subsequently be able to read them on a 360K drive again (unless you bulk erase and start all over again). WHen you write to a 360K disk using a 1.2Meg drive the erase/record head cuts a tunnel down the middle of the old 360K recording. This is fine as long as you only ever play back the disk on 1.2M drives. However if you try and read it on a 360K drive the head will pick up the 1.2Meg recording PLUS the residual unrerased 360K recording on each side resulting in a high probability of errors. The cardinal rule is this: If you must use 1.2M drives to make 360K d disks, make sure the disk is either new or bulk-erased, or that it has only ever been written to by a 1.2M drive in 360K format. Mike Gingell ....decvax!mcnc!ecsvax!mjg
stuart@bms-at.UUCP (12/11/86)
In article <2441@ecsvax.UUCP>, mjg@ecsvax.UUCP (Michael Gingell) writes: > In article <2690002@hplsla.HP.COM>, davidr@hplsla.HP.COM ( David Reed) writes: > > numbers of computers I use around here that: > > a 360K disc formatted in a 1.2M drive (with the /4 option to format as > > a 360K disc, of course) canNOT be read in about 1/3 of the 360K > > drives when a 1.2M drive also writes the data to the disc, but > > a 360K disc formatted in a 360K drive and written to by a 1.2M drive > > can NEARLY always be read in a 360K drive. > I would disagree with the above entirely. The above rules are either > accidentally reversed or a recipe for disaster. Disks made on 360k > drives should NEVER be written to with a 1.2 Meg drive if you want > to subsequently be able to read them on a 360K drive again (unless you [theoretical explanation deleted] This is all very fine in theory. In *practice*, however, our experience matches that of the original poster! Could there be something wrong with the theory? -- Stuart D. Gathman <..!seismo!dgis!bms-at!stuart>
burton@parcvax.UUCP (12/11/86)
The reason that theory apparently is contradicted by the "facts" is that the design of a floppy disk drive includes lots of slop for the distortions in the media caused by temperature and humidity. If you are doing interchange with other systems in the same area as the original system, you eliminate most of the slop causes. Phil Burton Xerox Corp.
mjg@ecsvax.UUCP (Michael Gingell) (12/15/86)
> > I would disagree with the above entirely. The above rules are either > > accidentally reversed or a recipe for disaster. Disks made on 360k > > drives should NEVER be written to with a 1.2 Meg drive if you want > > to subsequently be able to read them on a 360K drive again (unless you > > This is all very fine in theory. In *practice*, however, our experience > matches that of the original poster! > > Could there be something wrong with the theory? There is nothing wrong with the theory. 80 track drives have a narrower erase/record track than 40 track disks in general. However, many newer 40 track hald height drives probably use improved heads which are somewherwhere in between the performance of older 40 track and old/new 80 track. Just because it works probably means you are having a run of luck. Sooner or later it will run out. You have been warned. Mike Gingell ....decvax!mcnc!ecsvax!mjg
ranger@ecsvax.UUCP (Rick N. Fincher) (12/15/86)
> > > I would disagree with the above entirely. The above rules are either > > accidentally reversed or a recipe for disaster. Disks made on 360k > > drives should NEVER be written to with a 1.2 Meg drive if you want > > to subsequently be able to read them on a 360K drive again (unless you > > [theoretical explanation deleted] > > This is all very fine in theory. In *practice*, however, our experience > matches that of the original poster! > > Could there be something wrong with the theory? We have an IBM PC/AT, a Zenith and NCR AT compatible. None of these machines reliably writes to 360K disks. Sometimes it will work, but sooner or later the people that do it come to me to get their blown disks fixed. Usually after the disk starts exhibiting problems it can't be recovered so all of the data is destroyed. The last thing we need are drives that destroy data. As far as the 1.2 meg drives go, I have difficulty getting them to read 1.2 meg disks created by another machine, both of the same brand and especially from machines of different brands. I have put warning labels on our machines to the effect that data will be destroyed if 360K disks are used on 1.2 meg drives (reading is OK, of course, but if you write to them, sooner or later you will have trouble). Rick Fincher ranger@ecsvax