lulu@ucrmath.UCR.EDU (david lu) (01/07/90)
Hi there! I just tried to format some 1.2 Meg, high density disks in my 360K drive (as 360K), and I got the following error message: Invalid media or Track 0 bad - disk unusable Now, I know that I can't format 360K disks to 1.2 Meg in a 1.2 Meg drive, but why can't I format 1.2 Meg disks to 360K in a 360K drive? I thought that "blank" disks are just that -- blank. They can be reformatted as long as the density is "thick" enought, right? BTW, I'm using DOS version 3.1, and the disks have been previously formatted to 1.2 Meg in 1.2 Meg drives. - David ---==lulu@ucrmath==--- just another bewildered college undergraduate.
cs4g6ag@maccs.dcss.mcmaster.ca (Stephen M. Dunn) (01/08/90)
In article <3226@ucrmath.UCR.EDU> lulu@ucrmath.UUCP (david lu) writes:
$I just tried to format some 1.2 Meg, high density disks in my
$360K drive (as 360K), and I got the following error message:
$ Invalid media or Track 0 bad - disk unusable
$Now, I know that I can't format 360K disks to 1.2 Meg in a
$1.2 Meg drive, but why can't I format 1.2 Meg disks to 360K
$in a 360K drive? I thought that "blank" disks are just that
$-- blank. They can be reformatted as long as the density is
$"thick" enought, right?
As you found out, trying to use 1.2M diskettes as 360K disks doesn't
work. I don't know the physical reason for this, but trust me - don't
do it. Even if you can get them to format, they won't last long before
you start getting a lot - and I mean a _lot_ - of errors on them.
As for doing it the other way round (buying 360K disks and formatting
them at 1.2M), I don't recommend it either. I've found that I can typically
get 700-800K on such a disk using PCTools PCFORMAT - the outer tracks can
handle the higher density, but the inner ones can't and have large numbers
of bad sectors. Fine, so what's the problem, you say? After a fairly
short while, these disks begin to experience large numbers of errors, too.
BTW, why would you want to use expensive (HD) disks when cheaper (DD)
ones will suffice?
--
Stephen M. Dunn cs4g6ag@maccs.dcss.mcmaster.ca
<std_disclaimer.h> = "\nI'm only an undergraduate!!!\n";
****************************************************************************
If it's true that love is only a game//Well, then I can play pretendjacobs@chocolate.it.udel.edu (michael jacobs) (01/09/90)
In article <3226@ucrmath.UCR.EDU> lulu@ucrmath.UUCP (david lu) writes: =>I just tried to format some 1.2 Meg, high density disks in my =>360K drive (as 360K), and I got the following error message: => => Invalid media or Track 0 bad - disk unusable => =>Now, I know that I can't format 360K disks to 1.2 Meg in a =>1.2 Meg drive, but why can't I format 1.2 Meg disks to 360K =>in a 360K drive? I thought that "blank" disks are just that =>-- blank. They can be reformatted as long as the density is =>"thick" enought, right? Having just had this problem, I asked around and it seems that High Density disks and Double Density disks (used for 360k) do have physical differences. On the High Density disks, there are only certain places for the sectors while the DD's are more flexible since there's less stuff to squeze together. Mike J | The Grey Sysop... | Phone...RING!...yep yep yep yep yep! |
jacobs@cs.utah.edu (Steven R. Jacobs) (01/09/90)
In article <7715@nigel.udel.EDU> jacobs@chocolate.it.udel.edu (michael jacobs) writes: >In article <3226@ucrmath.UCR.EDU> lulu@ucrmath.UUCP (david lu) writes: >=>I just tried to format some 1.2 Meg, high density disks in my >=>360K drive (as 360K), and I got the following error message: >=> >=> Invalid media or Track 0 bad - disk unusable >=> >=>Now, I know that I can't format 360K disks to 1.2 Meg in a >=>1.2 Meg drive, but why can't I format 1.2 Meg disks to 360K >=>in a 360K drive? I thought that "blank" disks are just that >=>-- blank. They can be reformatted as long as the density is >=>"thick" enought, right? > >Having just had this problem, I asked around and it seems that High Density >disks and Double Density disks (used for 360k) do have physical differences. >On the High Density disks, there are only certain places for the sectors >while the DD's are more flexible since there's less stuff to squeze >together. The person that told you this was either joking or making it up to disguise their ignorance. Physically, the two types of disks are similar, with oxide covering the entire surface of the disk. The difference is in the oxide itself. On the high density disks, the oxide is a different material which requires a stronger magnetic field to record information. The heads in many 360K drives are not designed to produce a strong enough magnetic field to record data on the high density floppies. -- Steve Jacobs ({bellcore,hplabs,uunet}!utah-cs!jacobs, jacobs@cs.utah.edu)
amichiel@rodan.acs.syr.edu (Michielsen) (01/09/90)
>In article <3226@ucrmath.UCR.EDU> lulu@ucrmath.UUCP (david lu) writes: >=>I just tried to format some 1.2 Meg, high density disks in my >=>360K drive (as 360K), and I got the following error message: >=> Invalid media or Track 0 bad - disk unusable If you hold a real 1.2 MB disk up to the light and look at it at about a 30 or 45 degree angle, you should be able to see a ring. In the read/write window at the outside edge of the floppy disk media. It's about .1 inch wide or so. That 'window' is what causes dos to reject the disk for formatting. If it weren't there it would be possible for 360K drive to corupt the disk with an attempted format. In some 1.2 drives it also is used to select the drive density initially. When I have a disk I'm not sure of I just look for that edge window & know instantly that it is a 1.2 MB disk. al
jacobs@chocolate.it.udel.edu (michael jacobs) (01/10/90)
In article <JACOBS.90Jan9093359@cmos.cs.utah.edu> jacobs@cs.utah.edu (Steven R. Jacobs) writes: =>In article <7715@nigel.udel.EDU> jacobs@chocolate.it.udel.edu (michael jacobs) writes: =>>In article <3226@ucrmath.UCR.EDU> lulu@ucrmath.UUCP (david lu) writes: =>>=>I just tried to format some 1.2 Meg, high density disks in my =>>=>360K drive (as 360K), and I got the following error message: =>>=> =>>=> Invalid media or Track 0 bad - disk unusable =>> =>>Having just had this problem, I asked around and it seems that High Density =>>disks and Double Density disks (used for 360k) do have physical differences. =>> =>The person that told you this was either joking or making it up to =>disguise their ignorance. Physically, the two types of disks are =>similar, with oxide covering the entire surface of the disk. The =>difference is in the oxide itself. On the high density disks, the =>oxide is a different material which requires a stronger magnetic =>field to record information. The heads in many 360K drives are =>not designed to produce a strong enough magnetic field to record =>data on the high density floppies. I'd call that a physical difference. It has to do with what the floppy is made of, not on just what the floppy drive is doing. Mike J | The Grey Sysop... | Phone...RING!...yep yep yep yep yep! |
jacobs@cs.utah.edu (Steven R. Jacobs) (01/11/90)
In article <7795@nigel.udel.EDU> jacobs@chocolate.it.udel.edu (michael jacobs) writes: >In article <JACOBS.90Jan9093359@cmos.cs.utah.edu> jacobs@cs.utah.edu (Steven R. Jacobs) writes: >=>In article <7715@nigel.udel.EDU> jacobs@chocolate.it.udel.edu (michael jacobs) writes: >=>>In article <3226@ucrmath.UCR.EDU> lulu@ucrmath.UUCP (david lu) writes: >=>>=>I just tried to format some 1.2 Meg, high density disks in my >=>>=>360K drive (as 360K), and I got the following error message: >=>>=> >=>>=> Invalid media or Track 0 bad - disk unusable >=>> >=>>Having just had this problem, I asked around and it seems that High Density >=>>disks and Double Density disks (used for 360k) do have physical differences. >=>> >=> On the high density disks, the >=>oxide is a different material which requires a stronger magnetic >=>field to record information. The heads in many 360K drives are >=>not designed to produce a strong enough magnetic field to record >=>data on the high density floppies. > > I'd call that a physical difference. It has to do with what the floppy > is made of, not on just what the floppy drive is doing. Sure, it is a physical difference, but the disk manufactures don't go to any extra trouble to make the high density disks unusable in 360K drives. If there were no physical (i.e. materials) differences between the two types of disks, everyone would use ordinary disks in the high density drives (this is possible, but not recommended). -- Steve Jacobs ({bellcore,hplabs,uunet}!utah-cs!jacobs, jacobs@cs.utah.edu)
keithe@tekgvs.LABS.TEK.COM (Keith Ericson) (01/11/90)
In article <1700@rodan.acs.syr.edu> amichiel@rodan.acs.syr.edu (Michielsen) writes: >>In article <3226@ucrmath.UCR.EDU> lulu@ucrmath.UUCP (david lu) writes: >>=>I just tried to format some 1.2 Meg, high density disks in my >>=>360K drive (as 360K), and I got the following error message: >>=> Invalid media or Track 0 bad - disk unusable > >If you hold a real 1.2 MB disk up to the light and look at it at about a 30 >or 45 degree angle, you should be able to see a ring. In the read/write window >at the outside edge of the floppy disk media. It's about .1 inch wide or so. >That 'window' is what causes dos to reject the disk for formatting. If it >weren't there it would be possible for 360K drive to corupt the disk with an >attempted format. In some 1.2 drives it also is used to select the drive >density initially. When I have a disk I'm not sure of I just look for that >edge window & know instantly that it is a 1.2 MB disk. > >al HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, HA, Thank you - I haven't had such a good laugh in a _looooooong_ time. (excuse any typo's - I'm having a difficult time seeing through the tears from the laughter!) But, "al," you should remember to attach the 'smileys' to these kinds of postings: there are _some_ folks who might think you're serious! Thanks again for the humor break! kEITHe
ted@helios.ucsc.edu (Ted Cantrall) (01/11/90)
In article <1700@rodan.acs.syr.edu> amichiel@rodan.acs.syr.edu (Michielsen) writes: > >If you hold a real 1.2 MB disk up to the light and look at it at about a 30 >or 45 degree angle, you should be able to see a ring. In the read/write window >at the outside edge of the floppy disk media. It's about .1 inch wide or so. ---- Have you checked several brands of disks? The brand of 1.2M disks we use have no trace of that "ring". And besides, how would the older technology of 360K know to look for a ring that was invented later?? -ted- ------------------------------------------------------------------------------- ted@helios.ucsc.edu | "The opinions are mine... (408)459-2110 | ...the facts are public domain." -------------------------------------------------------------------------------
cs4g6ag@maccs.dcss.mcmaster.ca (Stephen M. Dunn) (01/12/90)
In article <JACOBS.90Jan9093359@cmos.cs.utah.edu> jacobs@cs.utah.edu (Steven R. Jacobs) writes:
$>Having just had this problem, I asked around and it seems that High Density
$>disks and Double Density disks (used for 360k) do have physical differences.
$The person that told you this was either joking or making it up to
$disguise their ignorance. Physically, the two types of disks are
$similar, with oxide covering the entire surface of the disk. The
$difference is in the oxide itself. On the high density disks, the
$oxide is a different material which requires a stronger magnetic
$field to record information. The heads in many 360K drives are
$not designed to produce a strong enough magnetic field to record
$data on the high density floppies.
That sure sounds like a physical difference to me. And also, as I
understand it, it's actually the other way round. A 1.2M disk actually
uses a weaker magnetic field, which makes 360K disks written in a 1.2M
drive unreadable in many 360K drives.
If the problem was that 360K drive heads didn't generate strong enough
magnetic fields, then I should be able to format 1.2M floppies at 360K in
my 1.2M drive. Well, it doesn't work any better in that drive than it
does in my 360K drive.
--
Stephen M. Dunn cs4g6ag@maccs.dcss.mcmaster.ca
<std_disclaimer.h> = "\nI'm only an undergraduate!!!\n";
****************************************************************************
If it's true that love is only a game//Well, then I can play pretendjdudeck@polyslo.CalPoly.EDU (John R. Dudeck) (01/13/90)
>In article <JACOBS.90Jan9093359@cmos.cs.utah.edu> jacobs@cs.utah.edu (Steven R. Jacobs) writes: >$On the high density disks, the >$oxide is a different material which requires a stronger magnetic >$field to record information. The heads in many 360K drives are >$not designed to produce a strong enough magnetic field to record >$data on the high density floppies. In article <25AD7F7A.26599@maccs.dcss.mcmaster.ca> cs4g6ag@maccs.dcss.mcmaster.ca (Stephen M. Dunn) writes: >And also, as I >understand it, it's actually the other way round. A 1.2M disk actually >uses a weaker magnetic field, which makes 360K disks written in a 1.2M >drive unreadable in many 360K drives. No, Mr. Jacobs is right, and Mr. Dunn is wrong. The high density diskettes have a higher coercivity, which means that they require a higher magnetizing field to record on them. Many older 360 k drives do not have the needed recording field for high density floppies. > 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. I don't understand this. I format high density diskettes to 360 k in my 1.2M drive all the time. However, if the floppy already had been written on, either as a 1.2 M disk, or as a 360 k disk on a 360 k drive, then the garbage in between the tracks sometimes makes the disk unreadable on a 360 k drive. -- John Dudeck "You want to read the code closely..." jdudeck@Polyslo.CalPoly.Edu -- C. Staley, in OS course, teaching ESL: 62013975 Tel: 805-545-9549 Tanenbaum's MINIX operating system.
jacobs@cs.utah.edu (Steven R. Jacobs) (01/14/90)
In article <25AD7F7A.26599@maccs.dcss.mcmaster.ca> cs4g6ag@maccs.dcss.mcmaster.ca (Stephen M. Dunn) writes: > In article <JACOBS.90Jan9093359@cmos.cs.utah.edu> jacobs@cs.utah.edu (Steven R. Jacobs) writes: >$>Having just had this problem, I asked around and it seems that High Density >$>disks and Double Density disks (used for 360k) do have physical differences. [[[On the High Density disks, there are only certain places for the sectors [[[while the DD's are more flexible since there's less stuff to squeze [[[together. >$The person that told you this was either joking or making it up to >$disguise their ignorance. The part that had sounded like a "joke" to me was the part the you conveniently deleted from the previous message (which I've added back in, highlighted by "[[[" above). I even _said_ in my message that the two disk types are physically similar (see below). But the part about "certain places for the sectors" is absurd, since the magnetic material covers the entire disk. Granted, the surface of the disk is polished (especially on the high density disks) but there are no "special" places on these particular disks. >$Physically, the two types of disks are ^^^^^^^^^^ >$similar, with oxide covering the entire surface of the disk. The ^^^^^^^ >$difference is in the oxide itself. On the high density disks, the >$oxide is a different material which requires a stronger magnetic >$field to record information. > That sure sounds like a physical difference to me. And also, as I > understand it, it's actually the other way round. A 1.2M disk actually > uses a weaker magnetic field, which makes 360K disks written in a 1.2M > drive unreadable in many 360K drives. I was not claiming that there were no physical differences, I only intended to claim that the physical differences were nothing like what the original poster had been told. Besides, if there were no physical differences then all disks would work in all drives. > 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. This would imply that 1.2M drives cannot write data on 360K disks, but people do this all the time. 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). 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. 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. 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). -- Steve Jacobs ({bellcore,hplabs,uunet}!utah-cs!jacobs, jacobs@cs.utah.edu)
wb8foz@mthvax.cs.miami.edu (David Lesher) (01/14/90)
>This would imply that 1.2M drives cannot write data on 360K disks, but >people do this all the time. >The problem with formatting 1.2M floppies at 360K is the difference >in the width of the recording heads. Alas, more half facts. A little RTFMing would disclose that 1.2 meg drives change not just rotational speed when working with 360k diskettes, but write current, too. That's how they cope with the different permeability. See, for example, the schematic for the drives, or the controller. This does not, of course, solve the head width problem. It does solve the problem of writing to the 360k diskettes at all. -- A host is a host & from coast to coast...wb8foz@mthvax.cs.miami.edu no one will talk to a host that's close..............(305) 255-RTFM Unless the host (that isn't close)......................pob 570-335 is busy, hung or dead....................................33257-0335
U5533129@ucsvc.ucs.unimelb.edu.au (CARDIOLOGY, R.M.H.) (01/15/90)
In article <JACOBS.90Jan13171438@cmos.cs.utah.edu>, jacobs@cs.utah.edu (Steven R. Jacobs) writes: > 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. 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). This is BULLS**T! The greater density of a 1.44M floppy comes from writing more sectors per track, not from using any more tracks. 1.44M, 1.2M and 720k disks all use 80 tracks, with 18, 15 and 9 sectors per track (x2 sides) each. 360k disks use 40 tracks x 9 sectors / track (x2 sides). As far as I know, no one does writes to adjacent tracks. I don't know whether this would work, but it would be very easy to do (with a small TSR on int 13). Does anyone know any more about this? Peter S.
thomasr@cpqhou.UUCP (Thomas Rush) (01/15/90)
I have had trouble formatting fresh-out-of-the-box 1.2 meg disks to 360 K. What could cause this? thomas.
bill@bilver.UUCP (Bill Vermillion) (01/16/90)
In article <25AD7F7A.26599@maccs.dcss.mcmaster.ca> cs4g6ag@maccs.dcss.mcmaster.ca (Stephen M. Dunn) writes: >In article <JACOBS.90Jan9093359@cmos.cs.utah.edu> jacobs@cs.utah.edu (Steven R. Jacobs) writes: >$>Having just had this problem, I asked around and it seems that High Density >$>disks and Double Density disks (used for 360k) do have physical differences. >$The person that told you this was either joking or making it up to >$disguise their ignorance. Physically, the two types of disks are >$similar, with oxide covering the entire surface of the disk. The >$difference is in the oxide itself. On the high density disks, the >$oxide is a different material which requires a stronger magnetic >$field to record information. The heads in many 360K drives are >$not designed to produce a strong enough magnetic field to record >$data on the high density floppies. > > That sure sounds like a physical difference to me. And also, as I >understand it, it's actually the other way round. A 1.2M disk actually >uses a weaker magnetic field, which makes 360K disks written in a 1.2M >drive unreadable in many 360K drives. Well - you do have it backwards. The HD media use higher coercivity oxide. This requires a higher write current to be able to magnetize than the oxides used in standards disks. Because of the higher coercivity you are able to write the bits closer together without the associated problems of bit-shifting or self-erasure. If you try to format a regular disk as high density the higher write currents generate a greater flux field, and this field will erase the previous bits just written. If you are successful in writing high density to low density media, the bits will be so closely packed and the magnetic orientation of the particles so easy to change that adjacent bits will try to move away if they are magnetized the same way. This is the bit shifting phenomenon. Think of how like poles on a magnet repel each other. The bits on the disk try to do the same. > 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. When you try to format 360 on a 1.2 meg disk the reason is that you aren't driving the head with enough current. The current DOES vary depending on what you are trying to write. So when you try to format a high density disk as low density, the write currents aren't strong enough to overcome the higher coercivity of the HD disk. After all, the system thinks it has a low density disk in it and is using reduced write current. A 360k drive has only one one write level. The 1.2 meg drives writes at two different levels, that is why the 1.2 meg drives works as poorly on hd media when trying to format at 360 as does the 360k drive when using HD media. -- Bill Vermillion - UUCP: {uiucuxc,hoptoad,petsd}!peora!tarpit!bilver!bill : bill@bilver.UUCP
bill@bilver.UUCP (Bill Vermillion) (01/16/90)
In article <10280@saturn.ucsc.edu> ted@helios.ucsc.edu (Ted Cantrall) writes: >In article <1700@rodan.acs.syr.edu> amichiel@rodan.acs.syr.edu (Michielsen) writes: >> >>If you hold a real 1.2 MB disk up to the light and look at it at about a 30 >>or 45 degree angle, you should be able to see a ring. In the read/write window >>at the outside edge of the floppy disk media. It's about .1 inch wide or so. >---- >Have you checked several brands of disks? The brand of 1.2M disks we use have >no trace of that "ring". And besides, how would the older technology of >360K know to look for a ring that was invented later?? > -ted- The rings were designed to prevent the center of the disk from being chewed up by the hub rings. The original 5.25 drive design clamped the disk when the door was shut. An improperly centered diskette could have the edges of the center hole crimped. Later designs went to a steeper cone. When the 1.2 meg drives came out, they were all of the later technology. They rotated the drive when the diskette was inserted and automatically centered the diskette on the clamp ring. The HD diskettes don't need the re-inforcments, and while many of the 360s did, they really don't anymore unless you are using one of the old full-height 5.25" drives. -- Bill Vermillion - UUCP: {uiucuxc,hoptoad,petsd}!peora!tarpit!bilver!bill : bill@bilver.UUCP
poffen@molehill (Russ Poffenberger) (01/17/90)
In article <510@cpqhou.UUCP> thomasr@cpqhou.UUCP (Thomas Rush) writes: > > > I have had trouble formatting fresh-out-of-the-box 1.2 meg >disks to 360 K. What could cause this? > > >thomas. There has been a recent discussion regarding this subject just recently on the net. It appears as though the coating on 1.2M disks is such that it need a stronger magnetic field in order to be written to reliably. 360K drives do not have this capability. The other thing is, why whould you spend the money to get high density disks, just to format them to 360K? Russ Poffenberger DOMAIN: poffen@sj.ate.slb.com Schlumberger Technologies UUCP: {uunet,decwrl,amdahl}!sjsca4!poffen 1601 Technology Drive CIS: 72401,276 San Jose, Ca. 95110 (408)437-5254
psrc@pegasus.ATT.COM (Paul S. R. Chisholm) (01/19/90)
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.90Jan13171438@cmos.cs.utah.edu>, 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.
rkl@cbnewsh.ATT.COM (kevin.laux) (01/20/90)
In article <1700@rodan.acs.syr.edu>, amichiel@rodan.acs.syr.edu (Michielsen) writes: > If you hold a real 1.2 MB disk up to the light and look at it at about a 30 > or 45 degree angle, you should be able to see a ring. <stuff deleted> > When I have a disk I'm not sure of I just look for that > edge window & know instantly that it is a 1.2 MB disk. There's an easier way to tell a 1.2 MB floppy from a 360 K one. If the diskette has a hub ring/reinforcement then it's definitely a 360 K diskette. 1.2 MB diskettes have no hub ring on purpose to make it easier to distinguish them from 360 K ones. --rkl
jacobs@cs.utah.edu (Steven R. Jacobs) (01/20/90)
In article <4407@pegasus.ATT.COM> psrc@pegasus.ATT.COM (Paul S. R. Chisholm) writes: >In article <JACOBS.90Jan13171438@cmos.cs.utah.edu>, jacobs@cs.utah.edu >(Steven R. Jacobs) writes: >> 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. Yes, I really blew it on this point. >> 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. This would mean that the high density disks are 1.44M instead of 1.2M would it not? I believe the high density disks are 15 sectors/track while the 360K disks are 9 sectors/track. This, with twice as many tracks on the 1.2M floppies, accounts for the 1.2M size. > Paul S. R. Chisholm, AT&T Bell Laboratories -- Steve Jacobs ({bellcore,hplabs,uunet}!utah-cs!jacobs, jacobs@cs.utah.edu)
carlj@hpcvmb.cv.hp.com (Carl Johnson) (01/21/90)
from rkl@cbnewsh.ATT.COM (kevin.laux) / 9:27 am Jan 19, 1990 / > There's an easier way to tell a 1.2 MB floppy from a 360 K one. If >the diskette has a hub ring/reinforcement then it's definitely a 360 K >diskette. 1.2 MB diskettes have no hub ring on purpose to make it easier >to distinguish them from 360 K ones. > >--rkl >---------- Don't count on this. I have used 360K disks in the past that did not have the hub reinforcement ring, and I have some 1.2MB disks now that do have the hub reinforcement rings. I know they are 1.2 MB since my drive won't format 360K disks with 1.2MB. Carl Johnson
cs4g6ag@maccs.dcss.mcmaster.ca (Stephen M. Dunn) (01/22/90)
In article <JACOBS.90Jan19094503@cmos.cs.utah.edu> jacobs@cs.utah.edu (Steven R. Jacobs) writes:
$would it not? I believe the high density disks are 15 sectors/track
$while the 360K disks are 9 sectors/track. This, with twice as many
$tracks on the 1.2M floppies, accounts for the 1.2M size.
This is correct. For 5.25" disks, one can have 8 or 9 sectors per
track and one or two sides of 40 tracks under DOS with double-density
diskettes; with high-density ones, you get 15 sectors per track, 80
tracks per side, two sides. The various capacities you can get are
then 160K, 180K, 320K, 360K, and 1.2M.
--
Stephen M. Dunn cs4g6ag@maccs.dcss.mcmaster.ca
<std_disclaimer.h> = "\nI'm only an undergraduate!!!\n";
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"I want to look at life - In the available light" - Neil Peartpsrc@pegasus.ATT.COM (Paul S. R. Chisholm) (01/23/90)
In article <4407@pegasus.ATT.COM> psrc@pegasus.ATT.COM (Paul S. R. Chisholm; hey, that's me!) writes: > A 1.2M disk has exactly twice as many sectors per track, and twice as > many (narrower) tracks, as a 360K disk. In article <JACOBS.90Jan19094503@cmos.cs.utah.edu>, jacobs@cs.utah.edu (Steven R. Jacobs) writes: > This would mean that the high density disks are 1.44M instead of 1.2M > would it not? I believe the high density disks are 15 sectors/track > while the 360K disks are 9 sectors/track. This, with twice as many > tracks on the 1.2M floppies, accounts for the 1.2M size. The *good* news is, between the two of us, I think we've got it all figured out. 360K * 2 * (15/9) = 1.2M, and 720K * 2 = 1.44M. And no matter how you calculate storage, the coercivity of the high density disks makes them impossible to format in a low density drive. > 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.