jcmorris@mwunix.mitre.org (Joe Morris) (03/01/91)
s64421@zeus.usq.EDU.AU (house ron) writes: >I have often read that formatting and writing 360K drives in 1.2M 5.25" >drives is unreliable. I have now obtained such a drive, and tried it, >and it seems to work perfectly every time (even after trying the disks >on genuine 360K drives). Have the 1.2M drives got better lately, or >am I just lucky? Lucky. Whether or not you have a problem depends on both the drive you write the disk on, and the drive you read it on...especially the latter. If you write a 360K diskette on a 1.2 MB drive you shouldn't have any problem reading it on anybody's 1.2 MB drive. (This assumes that you formatted the 360K diskette at 360K and not at 1.2 MB, of course.) The problem will appear, if at all, when you try to read the diskette in a normal 360K drive. Case in point: I've got two machines on my desk: an ancient AT with two drives (one each 1.2 MB and 360K), and a NEC PowerMate/386 with a single dual-density drive. Because that's where the WP software is, I write my monthly reports on the NEC and put the files on disk to send up to the front office...but until she got a new PS/2 my secretary had an old XT/286 with only the old full-height DSDD drives. She could never read the diskettes written on the NEC box; I had to put them on the AT and rewrite them by copying the disks onto themselves in the DSDD drive. On the other hand, at home I've got a very-low-serial-number original PC with full-height drives which never have any problem reading 360K diskettes from dual-density drives...from any properly working drive. Like I said, lucky. Joe Morris
s64421@zeus.usq.EDU.AU (house ron) (03/01/91)
I have often read that formatting and writing 360K drives in 1.2M 5.25" drives is unreliable. I have now obtained such a drive, and tried it, and it seems to work perfectly every time (even after trying the disks on genuine 360K drives). Have the 1.2M drives got better lately, or am I just lucky? -- Regards, Ron House. (s64421@zeus.usq.edu.au) (By post: Info Tech, U.C.S.Q. Toowoomba. Australia. 4350)
tjr@cbnewsc.att.com (thomas.j.roberts) (03/01/91)
From article <jcmorris.667836478@mwunix.mitre.org>, by jcmorris@mwunix.mitre.org (Joe Morris): > s64421@zeus.usq.EDU.AU (house ron) writes: > >>I have often read that formatting and writing 360K drives in 1.2M 5.25" >>drives is unreliable. I have now obtained such a drive, and tried it, >>and it seems to work perfectly every time (even after trying the disks >>on genuine 360K drives). Have the 1.2M drives got better lately, or >>am I just lucky? > > Lucky. Whether or not you have a problem depends on both the drive you > write the disk on, and the drive you read it on...especially the latter. Yes, and no. The real key, when writing 360K diskettes on a 1.2 Meg drive is: HAS THIS DISKETTE EVER BEEN WRITTEN ON BY A 360K DRIVE, OR BY A 1.2 Meg drive as a 1.2 Meg DISKETTE ?? If the answer is yes, DO NOT use this particular diskette as a 1.2 Meg to 360 Kb transfer diskette, use another. If you follow the following simple rule, you will (probably) have no trouble at all transfering files from a 1.2 Meg drive to a 360 Kb drive: Format a blank diskette as 360 Kb on the 1.2 Meg drive. NEVER, NEVER, NEVER write on the diskette with anything byt a 1.2 Meg drive. (You can read it on either a 360 Kb or a 1.2 Meg drive). Use another (360 Kb) diskette to transfer from 360 Kb to 1.2 Meg drives (format it on the 360 Kb drive). The reason for this rule is simple geometry of the read/write heads of the two drive types: the 360 Kb drive has a head that is almost twice as wide as the head on the 1.2 meg drive. When the 1.2 Meg drive formats a diskette at 360 Kb, it writes EVERY OTHER TRACK (i.e. at 40 Tracks/inch, instead of its own 80 tracks/inch), with the appropriate bit density. Thus, as long as the space between those formatted tracks HAS NEVER been written, a 360 Kb drive can read the diskette, because there usually is enough signal to drive the head, and there is no erroneous (old) signal to confuse it. If a 360 Kb drive has EVER written to the diskette, then the space between the (360 Kb on 1.2 Meg drive) formatted tracks will contain data that is different from the desired data, and will sometimes cause data errors. The same applies if a 1.2 Meg drive had EVER written to the diskette as a 1.2 Meg diskette. In principle, a 360 Kb diskette formatted on a 1.2 Meg drive does NOT conform to the specifications of a 360 Kb drive; and is not guaranteed to be readable on the 360 K drive. In practice, it is close enough for most 360 K drives, and works quite well. Following the above rule I have transferred thousands of files between 1.2 Meg drives and 360 Kb drives, without a single error. Tom Roberts att!ihlpl!tjrob TJROB@IHLPL.ATT.COM
lpdjb@brahms.amd.com (Jerry Bemis) (03/02/91)
In article <s64421.667842231@zeus> s64421@zeus.usq.EDU.AU (house ron) writes: >I have often read that formatting and writing 360K drives in 1.2M 5.25" >drives is unreliable. I have now obtained such a drive, and tried it, >and it seems to work perfectly every time (even after trying the disks >on genuine 360K drives). Have the 1.2M drives got better lately, or >am I just lucky? > >-- >Regards, > >Ron House. (s64421@zeus.usq.edu.au) >(By post: Info Tech, U.C.S.Q. Toowoomba. Australia. 4350)
s64421@zeus.usq.EDU.AU (house ron) (03/04/91)
tjr@cbnewsc.att.com (thomas.j.roberts) writes: >> s64421@zeus.usq.EDU.AU (house ron) writes: >> >>>I have often read that formatting and writing 360K drives in 1.2M 5.25" >>>drives is unreliable. I have now obtained such a drive, and tried it, >>>and it seems to work perfectly every time (even after trying the disks >>>on genuine 360K drives). Have the 1.2M drives got better lately, or >>>am I just lucky? >> >The real key, when writing 360K diskettes on a 1.2 Meg drive is: > HAS THIS DISKETTE EVER BEEN WRITTEN ON BY A 360K DRIVE, > OR BY A 1.2 Meg drive as a 1.2 Meg DISKETTE ?? > If the answer is yes, DO NOT use this particular diskette > as a 1.2 Meg to 360 Kb transfer diskette, use another. >The reason for this rule is simple geometry of the read/write heads >of the two drive types: the 360 Kb drive has a head that is almost >twice as wide as the head on the 1.2 meg drive. When the 1.2 Meg This makes sense. I have had no trouble with my particular drives with disks formatted in either place. However, since posting, I reformatted a disk which was originally formatted on an HP125 CP/M machine, and I have had trouble with this disk. As their drives only placed 248K on the disk, things were probably even worse. Many thanks to all the people who posted or mailed me replies. Everyone basically agreed that I am living dangerously. I am now getting a real 360K drive added to my new machine, but until then I shall continue to risk it, as I can always go back to the 1.2M drive to recover my info. BTW, Why doesn't this same problem occur with 3.5" diskettes? -- Regards, Ron House. (s64421@zeus.usq.edu.au) (By post: Info Tech, U.C.S.Q. Toowoomba. Australia. 4350)
reichert@motcid.UUCP (Chuck KD9JQ) (03/05/91)
The newer 360K drives can read 360K disks formatted in the 1.2M drives. The problem comes when using the older 360K drives. The new drives have a better Signal / Noise (Sorry guys, I'm RF) Ratio, or to put it more simply, they have lower BIT Error Rates. When copying from 360K to 1.2M, 1.2 to 360, 1.44 to 360, 1.44 to 720, etc. use the DOS XCOPY command. This allows copying one format to another. Chuck Reichert KD9JQ
gettys@yacht.enet.dec.com (Bob Gettys) (03/05/91)
One way to re-use a floppy without getting into this problem is to bulk erase it with a bulk tape eraser. This destroys the 360k info allowing the 1.2meg sized info to be visible without the old 360k info in the "background". Typically (but not always!) you can use a virgin (or a reborn virgin via bulk erase) floppy to take data from a 1.2meg drive to a 360k drive if the disk is formated as a 360k disk with the 1.2meg drive. This lays down the narrow track without the interference of the wide track in the background. When it won't work it is the result of the signal (remember, there is less of it) is tto weak for the particular 360k drive you are trying to read it on. Also remember to NEVER NEVER write on the floppy with a 360k drive as this will lay down a wide data track that the 1.2meg drive won't be able to write over later. (Then it's time to bulk erase it again!) As for the 3.5 inch ones - the head is the same size on both. The tracks are just closer together on the 1.44meg than on the 720k. Thus the 1.44meg can read and write the correct sized track in the right place for a 720k floppy. /s/ Bob Gettys
mir@opera.chorus.fr (Adam Mirowski) (03/05/91)
In article <20713@shlump.nac.dec.com>, gettys@yacht.enet.dec.com (Bob Gettys) writes:
%%
%% As for the 3.5 inch ones - the head is the same size on both. The
%% tracks are just closer together on the 1.44meg than on the 720k. Thus
%% the 1.44meg can read and write the correct sized track in the right
%% place for a 720k floppy.
I think that every IBM/Atari/MSX 3.5 inch drive uses 80 tracks. With one-
side-9 sectors you get 360 Kb, with 2 sides-9 sectors you obtain 720Kb and
1.44 Mb diskettes have 18 sectors per track. I don't know about 2.88 Mb
drives.
--
Adam Mirowski, mir@chorus.fr (FRANCE), tel. +33 (1) 30-64-82-00 or 74
Chorus systemes, 6, av.Gustave Eiffel, 78182 Saint-Quentin-en-Yvelines CEDEXjars@coast.ucsd.edu (Juan A. Rodriguez-Sero) (03/07/91)
In article <4684@cocoa46.UUCP> reichert@motcid.UUCP (Chuck KD9JQ) writes: >The newer 360K drives can read 360K disks formatted in the 1.2M drives. >The problem comes when using the older 360K drives. The new drives have a >better Signal / Noise (Sorry guys, I'm RF) Ratio, or to put it more simply, I have formatted and written 360K discs in my old ('86 vintage) AT clone, and read them successfully in my son's oldish ('88 vintage) XT clone. If they are new blanks, no special treatment is necessary; if they have something written on them already, I pass them through a nice deletion utility, BULKERAS (as, if I don't, they will be unreadable). -- Juan Antonio Rodriguez-Sero | Part of maturity is taking responsibility Center for Coastal Studies-SIO| for what we do, no matter how we feel. jars%coast@ucsd.edu | (From "Even in Summer the ice doesnt's melt" (619) 450 - 1377 | by David K. Reynolds)
terry@theseas.ntua.gr (Eleftherios Simotas) (03/07/91)
gettys@yacht.enet.dec.com (Bob Gettys) writes: > One way to re-use a floppy without getting into this problem is to bulk >erase it with a bulk tape eraser. This destroys the 360k info allowing >the 1.2meg sized info to be visible without the old 360k info in the >"background". > Typically (but not always!) you can use a virgin (or a reborn virgin >via bulk erase) floppy to take data from a 1.2meg drive to a 360k drive >if the disk is formated as a 360k disk with the 1.2meg drive. This lays >down the narrow track without the interference of the wide track in the >background. When it won't work it is the result of the signal (remember, >there is less of it) is tto weak for the particular 360k drive you are >trying to read it on. I've wondered about the ability of a 1.2meg drive being able to reliably write info on 360k disks even if they have been used in a 360k drive. I am aware of the head width differences resulting in a 1.2meg drive overwriting only part of the track written by a 360k drive. Couldn't this problem be overcome by having the 1.2meg drive write every track twice ? (now it skips every other track when writing 360k format). I have done a bit of low level programming on PC's but I am not in position to write such a utility just to see if it would work. There is also the problem of signal strength. The 360k drives have much larger write currents resulting in a stronger signal. The 1.2meg ones having to cope with much higher bit densities use lower write currents coupled with better signal detection electronics. So there is a chance even by double writing the tracks that the 360k signal will still peek through. > /s/ Bob Gettys
tjr@cbnewsc.att.com (thomas.j.roberts) (03/09/91)
From article <1265@theseas.ntua.gr>, by terry@theseas.ntua.gr (Eleftherios Simotas): > gettys@yacht.enet.dec.com (Bob Gettys) writes: > > >> One way to re-use a floppy without getting into this problem is to bulk >>erase it with a bulk tape eraser. This destroys the 360k info allowing >>the 1.2meg sized info to be visible without the old 360k info in the >>"background". > >> Typically (but not always!) you can use a virgin (or a reborn virgin >>via bulk erase) floppy to take data from a 1.2meg drive to a 360k drive >>if the disk is formated as a 360k disk with the 1.2meg drive. This lays >>down the narrow track without the interference of the wide track in the >>background. When it won't work it is the result of the signal (remember, >>there is less of it) is tto weak for the particular 360k drive you are >>trying to read it on. > > I've wondered about the ability of a 1.2meg drive being able to reliably > write info on 360k disks even if they have been used in a 360k drive. > I am aware of the head width differences resulting in a 1.2meg drive > overwriting only part of the track written by a 360k drive. Couldn't > this problem be overcome by having the 1.2meg drive write every track > twice ? (now it skips every other track when writing 360k format). > I have done a bit of low level programming on PC's but I am not in > position to write such a utility just to see if it would work. > There is also the problem of signal strength. The 360k drives have much > larger write currents resulting in a stronger signal. The 1.2meg ones > having to cope with much higher bit densities use lower write currents > coupled with better signal detection electronics. > So there is a chance even by double writing the tracks that the 360k > signal will still peek through. >> /s/ Bob Gettys There's NO HOPE of getting higher signal strength by writing two 1.2-meg-width tracks in place of a single 360-kb-width track. To do so would require that the two separately-written identical tracks are aligned under the wider 360-kb-width head to within less than half a bit width. The bit width for a 360-kb diskette is (outer track): (circumference) / (# bits) = (3.14*5") / (9*512*8) = 0.00042" Aligning the rotational position of a diskette to within 0.0002 inches is not possible using the 1/8" (or so) diameter index hole. The whole point of the diskette format is to remove any necessity for aligning the diskette very accurately. Tom ROberts att!ihlpl!tjrob TJROB@IHLPL.ATT.COM