jdwhite@iastate.edu (White Jason David) (04/07/91)
In a recent catalog from The Software Labs, I saw an ad for a "Disk Doubler". It's a $34 piece of hardware that puts a hole in DD disks to make disk drives think that they're HD disks. Here are an excerpt from the ad: ...will convert your low cost 3 1/2" 720K disks to work at high cost 1.44MB disks with NO COMPROMISE in media reliability. [...] This is possible because there is no difference at all between the media in 720K and 1.44MB disks used today! ... This ad is EXTREMELY bogus! I can tell many horror stories of people who have attempted to do this, only to lose data in a matter of days. I know that there IS a diffenence in the type of media used in DD and HD disks, but this ad really surprised me. I'd like to know what you netters think of this ad. I hate to think of all the people out there that believe this ad. Please post your comments to the net.
c60b-1eq@web-1g.berkeley.edu (Noam Mendelson) (04/07/91)
In article <1991Apr6.170017.24990@news.iastate.edu> jdwhite@iastate.edu (White Jason David) writes: > In a recent catalog from The Software Labs, I saw an ad for a "Disk >Doubler". It's a $34 piece of hardware that puts a hole in DD disks to make >disk drives think that they're HD disks. Here are an excerpt from the ad: > ...will convert your low cost 3 1/2" 720K disks to work at high cost >1.44MB disks with NO COMPROMISE in media reliability. [...] This is possible >because there is no difference at all between the media in 720K and 1.44MB >disks used today! ... >This ad is EXTREMELY bogus! I can tell many horror stories of people who have >attempted to do this, only to lose data in a matter of days. I know that there >IS a diffenence in the type of media used in DD and HD disks, but this ad >really surprised me. I'd like to know what you netters think of this ad. >I hate to think of all the people out there that believe this ad. >Please post your comments to the net. Another important point is that these "disk doublers" do damage to your diskettes. If you punch a hole in the diskette, fragments from the cover may scratch the diskette surface. Some diskette drives (such as my 1.44M Mitsubishi) allow you to set DIP switches that turn off the sensor which recognizes 1.44M diskettes. That way every diskette will be recognized as 1.44M. I don't recommend this for two reasons: (a) only your machine will be able to read these diskettes; (b) 720K diskettes will probably not be recognized by the drive. And, of course, these 'faux' 1.44M diskettes will be less reliable than true 1.44M. The point? I am surprised how these companies stay in business, considering the inevitable law suits which they may face. And always read the fine print. +==========================================================================+ | Noam Mendelson ..!agate!ucbvax!web!c60b-1eq | "I haven't lost my mind, | | c60b-1eq@web.Berkeley.EDU | it's backed up on tape | | University of California at Berkeley | somewhere." |
zap@lysator.liu.se (Zap Andersson) (04/08/91)
THere is SOME thruth to this, however: Most diskette manifacturers use the same media for 1.44 and 720k disks. However, a test is done on each disk, and if it falls below a certain threshold in reliability, they go in the 720k bucket, otherwise they will become 1.44 Meg's..... Imagine this on memory chips.... if QA testing allows, they are 1Meg chips, if not, just 256k ;-) /Z -- * * * * * * * * * * * * * * * * * (This rent for space) * My signature is smaller than * Be warned! The letter 'Z' is Copyright 1991 * yours! - zap@lysator.liu.se * by Zap Inc. So are the colors Red, Green and * * * * * * * * * * * * * * * * * Greenish-yellow (Blue was taken by IBM) -- * * * * * * * * * * * * * * * * * (This rent for space) * My signature is smaller than * Be warned! The letter 'Z' is Copyright 1991 * yours! - zap@lysator.liu.se * by Zap Inc. So are the colors Red, Green and * * * * * * * * * * * * * * * * * Greenish-yellow (Blue was taken by IBM)
cur022%cluster@ukc.ac.uk (Bob Eager) (04/08/91)
In article <571@lysator.liu.se>, zap@lysator.liu.se (Zap Andersson) writes: > Most diskette manifacturers use the same media for 1.44 and 720k disks. > However, a test is done on each disk, and if it falls below a certain > threshold in reliability, they go in the 720k bucket, otherwise they > will become 1.44 Meg's..... This was true for single-sided vs. double sided disks, where the media used the same coating both sides. It's true for chips, too. It is NOT true for DD vs. HD disks - the actual magnetic coating has a different makeup. -------------------------+------------------------------------------------- Bob Eager | University of Kent at Canterbury | +44 227 764000 ext 7589 -------------------------+-------------------------------------------------
melby@daffy.yk.Fujitsu.CO.JP (John B. Melby) (04/09/91)
>Most diskette manifacturers use the same media for 1.44 and 720k disks. >However, a test is done on each disk, and if it falls below a certain >threshold in reliability, they go in the 720k bucket, otherwise they >will become 1.44 Meg's..... This depends on which disks you are referring to. This would be the case for double-sided and single-sided high-density disks, but from what I have heard, most manufacturers use separate processes for high-density disks and "ordinary" disks ([12]D and [12]DD). >* Be warned! The letter 'Z' is Copyright >* by Zap Inc. So are the colors Red, Green >* Greenish-yellow (Blue was taken by IBM) Ah, so that explains the "technically unfeasible" story for blue LED's :-) :-) ... * standard disclaimers apply * ----- John B. Melby Fujitsu Limited, Machida, Japan melby%yk.fujitsu.co.jp@uunet
steved@hrshcx.csd.harris.com (Steve Daukas) (04/09/91)
In article <22191.28006b16@cluster@ukc.ac.uk> cur022%cluster@ukc.ac.uk (Bob Eager) writes: >In article <571@lysator.liu.se>, zap@lysator.liu.se (Zap Andersson) writes: >> Most diskette manifacturers use the same media for 1.44 and 720k disks. >> However, a test is done on each disk, and if it falls below a certain >> threshold in reliability, they go in the 720k bucket, otherwise they >> will become 1.44 Meg's..... >This was true for single-sided vs. double sided disks, where the media >used the same coating both sides. It's true for chips, too. It is NOT true >for DD vs. HD disks - the actual magnetic coating has a different makeup. However, this tatic still works fine! I have been doing this for years with so few failures, I get surprised when they do happen. The magnetic coating may be a different composition, but the DD holds HD data just fine (I have some disks from 1986 that still read perfectly well). Steve -- .-------------------..-------------------------. | Stephen C. Daukas || sdaukas@csd.harris.com | | (617) 221-1834 || uunet!hcx1!misg!sdaukas | `-------------------'`-------------------------'
buckland@cheddar.ucs.ubc.ca (Tony Buckland) (04/09/91)
In article <1991Apr6.234019.2894@agate.berkeley.edu> c60b-1eq@web-1g.berkeley.edu (Noam Mendelson) writes: >The point? I am surprised how these companies stay in business, considering >the inevitable law suits which they may face. And always read the fine >print. 1. There's one born every minute (customers who hunger for a free lunch). 2. There's one born every minute (companies with the same personnel, but different names); i.e., to sue them, you have to find them.
slandrum@ntg.uucp (Stephen Landrum) (04/09/91)
In article <571@lysator.liu.se> zap@lysator.liu.se (Zap Andersson) writes: >THere is SOME thruth to this, however: > >Most diskette manifacturers use the same media for 1.44 and 720k disks. >However, a test is done on each disk, and if it falls below a certain >threshold in reliability, they go in the 720k bucket, otherwise they >will become 1.44 Meg's..... > >Imagine this on memory chips.... if QA testing allows, they are 1Meg >chips, if not, just 256k ;-) Well, your reference to memory chips is not as silly as it seems. Back when RAM was expensive, Atari sold 8k boards for their Atari 800 computer which were filled with 16K RAMs that had errors in only one half of the address space, and one of the address lines would be tied low or high depending on which half was bad. -- Stephen H. Landrum VOICE: (415) 813-8909 UUCP: ...apple!ntg!slandrum USNAIL: New Technologies Group Inc. 2468 Embarcardero Way, Palo Alto CA 94303
bill@bilver.uucp (Bill Vermillion) (04/09/91)
In article <571@lysator.liu.se> zap@lysator.liu.se (Zap Andersson) writes: >THere is SOME thruth to this, however: > >Most diskette manifacturers use the same media for 1.44 and 720k disks. >However, a test is done on each disk, and if it falls below a certain >threshold in reliability, they go in the 720k bucket, otherwise they >will become 1.44 Meg's..... > The testing you mentioned used to be done to separate Single Sided from Double sided, back when a goo 88k 5.5" disk cost $5.00 each. Get some spec sheets from a diskette manufacturer and you will see that there ARE differences in the magnetic media between DD and HD. Typically the DD's are about 600 oersted coercivity while the HDs are in the 700 oersted range. The problem with ad's like that is they perpetutate falsehoods. A little over a year ago Jerry Pournelle espoused the same thing in his Byte article. He could have easily picked up the phone an called Sony (one of the larger 3.5" disk mfrs) and gotten the correct information, but he just said the same thing you did. I have spec sheets from at least BASF and CENTEC and there ARE differences, not matter what the ad's say. You can get by with this (sometimes) better than those who tried to use 360's at 1.2 meg in the 5.25" world. Those are about 300 oersteds for the DD's and 600 for the HD's. As a matter of fact the 5.25" HD media is just about identical to the 3.5" DD media. -- Bill Vermillion - UUCP: uunet!tarpit!bilver!bill : bill@bilver.UUCP
chao@oahu.cs.ucla.edu (Chia-Chi Chao) (04/09/91)
In article <1991Apr9.042503.18670@bilver.uucp> bill@bilver.uucp (Bill Vermillion) writes: >Typically the DD's are about 600 oersted coercivity while the HDs >are in the 700 oersted range. > >You can get by with this (sometimes) better than those who tried to >use 360's at 1.2 meg in the 5.25" world. Those are about 300 >oersteds for the DD's and 600 for the HD's. As a matter of fact >the 5.25" HD media is just about identical to the 3.5" DD media. I totally agree with these points. 3.5" DD disks can be formatted to HD most of the time because the coercivities between DD and HD are much smaller than those between 5.25" DD and HD. Look at the MEI/Micro catalog. They have these numbers listed. The following was obtained from one of the newsgroups a few years(?) ago. That is the most technical explanation I have seen. ============================================================ >From: tim@j.cc.purdue.edu (Timothy Lange) Organization: PC Learning Resource Center, Purdue University I get questions concerning the differences between double sided, double density (DS/DD) disks versus double sided, high density (DS/HD) disks and double sided, quad density (DS/QD) disks. To explain these differences I would like to come up with a chart or table to explain what is going on and what works with what. To save my fingers and space, from now on DD means Double Density, QD means Quad Density, HD means High Density, SS means Single Sided, and DS means Double Sided. So far I have the following table for 5.25" diskettes used on IBM PC: Disk Drive Type: PC Drive Type: AT Type IO Freq-48 TPI IO Freq-48 TPI / IO Freq-96 TPI / CO Freq-96 TPI SS/DD 180K 180K*1 / 180K*2 / Note *3 DS/DD 360K 360K*1 / 720K*2 / Note *3 DS/QD 360K 360K*1 / 720K / Note *3 DS/HD Note *4 Note *4 / Note *4 / 1.2MB The IO and CO Freq means using the frequency for Iron Oxide or Chromium Oxide. The TPI abbreviation means Tracks per Inch. *1 Track width and alignment may cause problems when used on other drives. *2 Disk not be certified for this track density. *3 Iron Oxide media not compatible with this frequency. *4 Chromium Oxide media not compatible with this frequency. So far I have the following table for 3.5" diskettes used on IBM PC: Disk Drive Type: model 30 Drive Type: model 50 Type IO Freq-135 TPI IO Freq-135 TPI / CO Freq-135 TPI DS/DD 720K 720K / Note *1 DS/HD Note *2 Note *2 / 1.44MB *1 Iron Oxide media not compatible with this frequency. *2 Chromium Oxide media not compatible with this frequency. I know that HD drives can deal with DD floppies by changing the recording frequency to match the oxide used on the media and the track to track distances. At format time, the drives do not know what kind of disk is in them, you have to tell it with formatting options. Once the disk has been formatted though, the drive will figure out what it is, if it is capable of supporting the media being used. A DD drive can handle DD and QD disks, a QD drive can handle DD and QD disks, and a HD drive can handle DD, QD, and HD. You should NOTE try to exceed the certification of the disk, i.e., use a SS disk as DS, use a DD disk as QD or HD, use a QD disk as HD, or a HD disk as DD or QD. If the disk is marked as SS that means the manufacturer has certified only one side for use. The other problems are recording frequency/Oersted versus media oxide type mismatch. What is a QD disk by definition? From what I have been told, it is basically a DD disk certified at the 96 TPI track density. Here are some other facts: DD and QD disks have an Iron oxide media, HD disks have a Chromium oxide media. DD and QD are recorded at 300 Oersted, HD disks are done at 670 Oersted. A DD disk has two sides, each having 40 tracks, each track having 9 sectors, each sector having 512 bytes. A QD disk just has 80 tracks per side, (but you can raise the number of sectors per track, example, 10 sectors per track would give you 810K for disk space, non-IBM then, if ever). A HD disk, has two sides, each having 80 tracks, each track having 15 sectors, each sector having 512 bytes. IBM compatible machines use soft sectored disks, this means at format time the software writes it own sector marks on the disk instead of using hard sectors which are defined by timing holes in the disk itself. ---------- Oersted. The cgs emu of magnetic intensity exists at a point where a force of 1 dyne acts upon a unit magnetic pole at that point, i.e., the intensity 1 cm from a unit magnetic pole. Purdue U. Computing Center/MATH Bldg./W. Lafayette, IN 47907/317-494-1787 Arpanet=tim@j.cc.purdue.edu CIS=75410,525 Bitnet=TIM@PURCCVM -- Chia-Chi Chao chao@cs.ucla.edu ..!ucbvax!cs.ucla.edu!chao
hdrw@ibmpcug.co.uk (Howard Winter) (04/09/91)
It was written as a joke, but actually it used to happen: Memory chips were made which had more cpaacity than was needed in the finished chip, and the different banks were tested. Depending on which banks had faults, the connection from the chip to the package was made, so that the good banks were being used, the bad ones weren't. Nowadays I don't think they do this. BTW I understand the medium used in DD vs HD disks IS different, and that the coercivity (the ease with which magnetism becomes permanent) is the variable. I have certainly never been able to reformat an HD 3.5" to 1.44 once it has been formatted at 720, and I believe that the switching of strength of magnetism used is the reason - the weaker HD field cannot overcome the 720. But I may be wrong... Howard. -- Automatic Disclaimer: The views expressed above are those of the author alone and may not represent the views of the IBM PC User Group. -- hdrw@ibmpcug.Co.UK Howard Winter 0W21' 51N43'
paixao@ug.cs.dal.ca (Nuno M. Paixao) (04/09/91)
I have no technical information to relay to you, just something I learned from experience. I was using a machine with a high density 3.5" floppy in it, and wasn't aware that it was high density. Whenever I formatted a disk ( a DS/DD) I simply typed FORMAT. The machine then formatted them to High density. While using that machine, I could store 1.4MB of information on that disk, bu then I tried to take one of those disks to another machine. Neither a low density nor a high density floppy could read my disks ( and there were about 12 of them.) Since I had lost access to the orginal machine, I lost over 10 MB of stuff. I wasn't impressed. :-( The point of the story is: If your disk says DS/DD format it to 720K. If it says DS/HD then format it to 1.44MB. In the long run, you will be glad you did. Nuno -- *----------------------*---------------------------*------------------------* | Nuno M. Paixao | paixao@ug.cs.dal.ca | dexter@ac.dal.ca | *----------------------*---------------------------*------------------------* | McIntosh Jr ... The Power to Crush the other Kids!!! (SNL) |
peter@cunixf.cc.columbia.edu (Peter Wu) (04/10/91)
[ Lots of stuff on disks and various magnetic media ... ] Aren't you guys taking the newsgroup name just a little bit too literally? :) PQ? --------------------------------------------------------------------------- Pedro Quien? peter@cunixf.cc.columbia.edu Peter K. Wu ---------------------------------------------------------------------------
public@cc.tut.fi (PD Software Group) (04/10/91)
In article <1991Apr9.141703.5134@cs.dal.ca> paixao@ug.cs.dal.ca (Nuno M. Paixao) writes: >I was using a machine with a high density 3.5" floppy in it, and wasn't aware >that it was high density. Whenever I formatted a disk ( a DS/DD) I simply >typed FORMAT. The machine then formatted them to High density. There are some 3.5" drives which can't determine if the disk is DD or HD. Such drives are used at least on IBM PS -computers. > >While using that machine, I could store 1.4MB of information on that disk, >bu then I tried to take one of those disks to another machine. Neither >a low density nor a high density floppy could read my disks ( and there were >about 12 of them.) Since I had lost access to the orginal machine, >I lost over 10 MB of stuff. I wasn't impressed. :-( That was because the drive with you formatted the disks couldn't determine if the disk is DD. The other drive noticed that the disk you had formatted with previous drive does not have the HD hole. So it thought that disk is DD and failed to read it since the sectors on DD and HD disks are different size (both DD and HD can contain 512 bytes, but on DD there are 9 sectors per track when HD has 18 sectors per track). Since you dont have access to that original machine, you could try this (I mean if you still have those disks): Make a hole to DD disk at the same location than on the HD disk's HD hole is and try then read the disk on the HD drive. It should be usable again. >The point of the story is: > If your disk says DS/DD format it to 720K. > If it says DS/HD then format it to 1.44MB. I disagree with this. Whatever the manufacturers say about the differences with the media of DD and HD disks (I admit that most likely there is some differences between DD and HD disks), it is quite reliable to use 'hand-made-HDs'. A friend of mine has used such disks for YEARS without problems - nowadays he has 900-1000 hand-made (and even nameless) DD-HDs -- Tapio Keih{nen | "Whenever you dream Mesihein{nkatu 2 B 6 | you're holding the key, 33340 Tampere, Finland | it opens the door public@cc.tut.fi | to let you be free" - RJD '85
david@kessner.denver.co.us (David Kessner) (04/10/91)
In article <1991Apr9.075828.2135@ibmpcug.co.uk> hdrw@ibmpcug.co.uk (Howard Winter) writes: >BTW I understand the medium used in DD vs HD disks IS different, >and that the coercivity (the ease with which magnetism becomes >permanent) is the variable. I have certainly never been able to >reformat an HD 3.5" to 1.44 once it has been formatted at 720, >and I believe that the switching of strength of magnetism used >is the reason - the weaker HD field cannot overcome the 720. > >But I may be wrong... > >Howard. The HD disks are different from the DD disks... I dont know why this is really a question. I mean, just look at them! HD disks are darker and more highly "polished". DD disks are rather dull... I have always had a problem reformatting disks at a different density, I dont know why. Using a big magnet or a bulk eraser will fix the problem, however... I for one will never use disks beyond their rating (ie, using DD as HD, or SS as DS). While it may work for the most part, you do get more errors than normal-- perhapse only one critical error every 10-20 disks but you never know WHEN that error will pop up. I'd rather have some piece of mind, rather than play Russian Roulette... -- David Kessner - david@kessner.denver.co.us | do { 1135 Fairfax, Denver CO 80220 (303) 377-1801 (p.m.) | . . . If you cant flame MS-DOS, who can you flame? | } while( jones);
landers@zeus.mgmt.purdue.edu (Christopher Landers) (04/11/91)
In article <1991Apr9.141703.5134@cs.dal.ca> paixao@ug.cs.dal.ca (Nuno M. Paixao) writes: >I have no technical information to relay to you, just something I learned >from experience. Not to flame the author, but the net in general. This is no help! This thread has been going on for a while with answres Yes you can and No you can't. I've yet to see much authorative discussion on the subject, and I'm very interested. At least this author admits up front that he's just expressing opinions based upon experence. CAN SOMEONE WITH HARD FACTS ANSWER THIS QUESTION?!? -- <================================><===============================> || Christopher Landers || PURDUE UNIVERSITY - KRAN 708 || || Krannert Computing Center || West Lafayette, IN 47907 || <=================== landers@zeus.mgmt.purdue.edu ================>
david@kessner.denver.co.us (David Kessner) (04/11/91)
In article <1991Apr11.005743.1000@zeus.mgmt.purdue.edu> landers@zeus.mgmt.purdue.edu (Christopher Landers) writes: >CAN SOMEONE WITH HARD FACTS ANSWER THIS QUESTION?!? > > <=================== landers@zeus.mgmt.purdue.edu ================> The hard facts are on the disk itself. One says DD, and the other says HD. Most disks have a warranty on them for error-free use-- and using a DD disk as HD void this warranty. Thus, the manufacturer makes no claims on if a DD disk will work as HD. That's the fact. Using a DD disk as HD disk comes with no guarrentes. If there were hard facts supporting this then all the disk manufacturers would re-label the disks and sell them at a higher price... If you want hard facts, read the box that the disks comes in. Those are the only facts that are backed by more than "I've tried it and it seems to work." -- David Kessner - david@kessner.denver.co.us | do { 1135 Fairfax, Denver CO 80220 (303) 377-1801 (p.m.) | . . . If you cant flame MS-DOS, who can you flame? | } while( jones);
gerardka@hobbes.ism.isc.com (gerard) (04/11/91)
In article <1991Apr11.005743.1000@zeus.mgmt.purdue.edu> landers@zeus.mgmt.purdue.edu (Christopher Landers) writes: >In article <1991Apr9.141703.5134@cs.dal.ca> paixao@ug.cs.dal.ca (Nuno M. Paixao) writes: >>I have no technical information to relay to you, just something I learned >>from experience. > >Not to flame the author, but the net in general. This is no help! > >This thread has been going on for a while with answres Yes you can >and No you can't. I've yet to see much authorative discussion on >the subject, and I'm very interested. At least this author admits up >front that he's just expressing opinions based upon experence. > >CAN SOMEONE WITH HARD FACTS ANSWER THIS QUESTION?!? > I have a copy of a "Floppy (3.5" HD) Disk Quality Report" put out by MEMCON Corp., a diskette duplicating service. They evaluated 21 brands of high density diskettes for 11 parameters, including: dropouts, extra pulses, peak shift, amplitude and resolution, variation of modulation, overwrite capability. For each parameter, a score was assigned (10=excellent, 6=avg, 2=poor). Seven brands had a weighted total score > 80, and rated "good" (Sony, Fuji, 3M, Kodak, Memorex, BASF, Maxell). Three brands had a score < 65, and were rated "poor" (Opus, Kao, Centech). The high total was 83.4 (Sony); the low was 49.7 (Centech). No brand stood out in all tests. MEMCON states that HD floppies differ from DD in coating thickness and magnetic properties. A 2MB drive cannot completely saturate the mag coating on a 1MB diskette. "A DD floppy should never be substituded for a HD". Given that real HD floppies barely conform to ANSI standards why risk your data? Gerard
michaely@uhunix1.uhcc.Hawaii.Edu (Michael Masao Yokoyama) (04/11/91)
Ahem!!!!!!!! Does this group talk about media or multimedia? -- Michael M. Yokoyama Graduate Student; University of Hawaii michaely@uhccux.uhcc.Hawaii.EDU 21 deg. 19' N; 157 deg. 52' W
jpc@fct.unl.pt (Jose Pina Coelho) (04/11/91)
In article <1991Apr10.075541.638@kessner.denver.co.us> david@kessner.denver.co.us (David Kessner) writes: [......] I for one will never use disks beyond their rating (ie, using DD as HD, or SS as DS). While it may work for the most part, you do get more errors than normal-- perhapse only one critical error every 10-20 disks but you never know WHEN that error will pop up. I'd rather have some piece of mind, rather than play Russian Roulette... Why ? Do you have your mind backed up in a floppy ? -- Jose Pedro T. Pina Coelho | BITNET/Internet: jpc@fct.unl.pt Rua Jau N 1, 2 Dto | UUCP: ...!mcsun!unl!jpc 1300 Lisboa, PORTUGAL | Home phone: (+351) (1) 640767 - If all men were brothers, would you let one marry your sister ?
lstowell@pyrnova.pyramid.com (Lon Stowell) (04/12/91)
In article <1991Apr11.005743.1000@zeus.mgmt.purdue.edu> landers@zeus.mgmt.purdue.edu (Christopher Landers) writes: > >This thread has been going on for a while with answres Yes you can >and No you can't. I've yet to see much authorative discussion on >the subject, and I'm very interested. At least this author admits up >front that he's just expressing opinions based upon experence. > >CAN SOMEONE WITH HARD FACTS ANSWER THIS QUESTION?!? Yes. Take some of YOUR most critical data....the type that could potentially cost YOU your job, life, etc. Take a 720 Kb diskette and format it to 1.44 Mbyte. [Or the equivalent in 5"]. Record your critical data on this mis-formatted diskette [ simply a cheapskate's attempt to save a dollar or so ] then destroy all other copies. Sometime later, when you ABSOLUTELY NEED this critical data, hope and pray that your miserliness hasn't just cost you your job, life, etc. Any further questions? (Yes, I know that anecdotally it is possible to mis-use SOME manufacturer's diskettes to save a few pennies. Although this example is extreme, if you can afford the computer, likely the data on the diskette is worth more than the few pennies you would save. If you have the pre-req technical knowledge to know whether or not this mis-use is actually safe, you would also know enough not to attempt it.)
buckland@cheddar.ucs.ubc.ca (Tony Buckland) (04/12/91)
In article <JPC.91Apr11105328@terra.fct.unl.pt> jpc@fct.unl.pt (Jose Pina Coelho) writes: >In article <1991Apr10.075541.638@kessner.denver.co.us> >david@kessner.denver.co.us (David Kessner) writes: > ... I'd rather have some piece of mind, rather > than play Russian Roulette... Actually, you can get all the pieces of mind you want *by* playing Russian Roulette. All over the walls and the furniture.
sfp@mars.ornl.gov (Phil Spelt) (04/12/91)
In article <1991Apr6.170017.24990@news.iastate.edu> jdwhite@iastate.edu (White Jason David) writes: > > In a recent catalog from The Software Labs, I saw an ad for a "Disk >Doubler". It's a $34 piece of hardware that puts a hole in DD disks to make >disk drives think that they're HD disks. Here are an excerpt from the ad: > > ...will convert your low cost 3 1/2" 720K disks to work at high cost >1.44MB disks with NO COMPROMISE in media reliability. [...] This is possible >because there is no difference at all between the media in 720K and 1.44MB >disks used today! ... > > >This ad is EXTREMELY bogus! I can tell many horror stories of people who have >attempted to do this, only to lose data in a matter of days. I know that there >IS a diffenence in the type of media used in DD and HD disks, but this ad >really surprised me. I'd like to know what you netters think of this ad. >I hate to think of all the people out there that believe this ad. >Please post your comments to the net. At least in the past, it is my understanding that disk surfaces are inspected at manufacture to ascertain their integrity. Those that "pass" are used in the HD disks, those that do not are used in DD disks. HD information storage requires *MUCH* more of the medium's magnetic surface than does DD, so I agree with this posting, and had the same skepticism for that ad! There really "Ain't no free lunch"!!! ============================================================================= MIND. A mysterious form of matter secreted by the brain. Its chief activity consists in the endeavor to asscertain its own nature, the futility of the attempt being due to the fact that it has nothing but itself to know itself with. -- Ambrose Bierce ============================================================================= Phil Spelt, Cognitive Systems & Human Factors Group sfp@epm.ornl.gov ============================================================================ Any opinions expressed or implied are my own, IF I choose to own up to them. ============================================================================
bill@bilver.uucp (Bill Vermillion) (04/13/91)
In article <1991Apr9.065832.16253@cs.ucla.edu> chao@oahu.cs.ucla.edu (Chia-Chi Chao) writes: >In article <1991Apr9.042503.18670@bilver.uucp> bill@bilver.uucp (Bill Vermillion) writes: >>Typically the DD's are about 600 oersted coercivity while the HDs >>are in the 700 oersted range. >>You can get by with this (sometimes) better than those who tried to >>use 360's at 1.2 meg in the 5.25" world. Those are about 300 >>oersteds for the DD's and 600 for the HD's. As a matter of fact >>the 5.25" HD media is just about identical to the 3.5" DD media. >I totally agree with these points. 3.5" DD disks can be formatted to HD most >of the time because the coercivities between DD and HD are much smaller than >those between 5.25" DD and HD. Look at the MEI/Micro catalog. They have these >numbers listed. >The following was obtained from one of the newsgroups a few years(?) ago. That >is the most technical explanation I have seen. >============================================================ >>From: tim@j.cc.purdue.edu (Timothy Lange) >Organization: PC Learning Resource Center, Purdue University >I know that HD drives can deal with DD floppies by changing the recording >frequency to match the oxide used on the media and the track to track ^^^^^^^^^^ >distances. It is not just the frequency of the data transfer that changes. The write current is increased to be able to record on the HD media. The coercivity is the key. The higher the coercivity the stronger the write current needed. (Think of the root of the word coerce, sometimes used to mean force). It takes more "persuasion" to "force" the data onto an HD disk. The problems with trying to write on a media not supported are two-fold. Trying to write 360k type data onto and HD disk results in too little current being applied and the disk can not be "coerced" into accepting the data. The opposite happens when trying to write HD (1.2 megs) onto a standard disk. Too much current is being applied. The standard media has a lower corecivity and the higher write current causes self-erasure. This is because the higher current generates a higher magnetic field. These are not finite fields, but decrease with distance. A bit will be written to a disk, the disk rotates enought to place the next bit into position. The higher current on the HD write extends the magenetic field far enough to partially (or wholly) erase the previously written bit. You can typically get the first 20 to 30 tracks on a std media written with an HD format, but as the writing circumference becomes smaller as the head moves closer to the center of the disk, the bits are physically spaced closer together and self-erasure starts. Disks are designed to be reliable at the smallest circumference. Another thing to note with 3.5" disks writing at 135 tpi is that the track length at the outer track is not as drastically different from the inner track as it is in the 5" media. On an older format, 8" floppies, which were written at 48 tpi (same as the 5" disks), the 77 tracks were quite long. The shortest track on those was about the length of the longest on the 5" disk. The problems with putting more information on the 8" disks, with such things as more tracks per inch, was that the media was so large, that centrifugal force came into play and caused the disk to stretch outward slightly causing track mis-alginment. The only people who successfully got around this (to my knowledge) were the folks at Bernouli, who put an embedded servo on their disks to get 10 megs on 8" inch media. Embedding a servo on a data track takes up valuable space. In the 3.5 inch world Brier is recording the servo track BENEATH the data track to get 25 MEGS on a 3.5 floppy. They can do this because on of the properties of magnetic media is that the shorter the wavelength the closer to the surface of the media the signal is written. By using a lower frequency for the servo track, the higher frequency data track can be written in the same place and both can read. Got a bit off the track, but I think it was pertinent. bill -- Bill Vermillion - UUCP: uunet!tarpit!bilver!bill : bill@bilver.UUCP
bill@bilver.uucp (Bill Vermillion) (04/13/91)
In article <1991Apr9.191024.7048@cc.tut.fi> public@cc.tut.fi (PD Software Group) writes: > >In article <1991Apr9.141703.5134@cs.dal.ca> paixao@ug.cs.dal.ca (Nuno M. Paixao) writes: >>I was using a machine with a high density 3.5" floppy in it, and wasn't aware >>that it was high density. Whenever I formatted a disk ( a DS/DD) I simply >>typed FORMAT. The machine then formatted them to High density. >There are some 3.5" drives which can't determine if the disk is DD or >HD. Such drives are used at least on IBM PS -computers. It is NOT the drive that is the problem in the PS computers, it is the implementation. IBM PS-2's look at the media to determine it is formatted or not, and then proceed to format at the default unless you specify differently. Other implementations look at the media housing to deterimine density by seeingif the extra hole is there. You can format 720's all day long at 1.44 in a PS2 environment. One interesting sidelight showing the differences between implementation in SOFTWARE on the same piece of harware was an IBM 80 I installed in a Xenix application. The floppy drive was defective. But you would not know this under DOS. You would type format with NO DISK under DOS and it would reject the format command. Under Xenix you would type format, the drive would turn on, the drive would step all 80 tracks, and you would watch it through the door. The hardware sensor indicating disk/no-disk failed in the disk in mode. But IBM never checked that, as they don't check the density hole. -- Bill Vermillion - UUCP: uunet!tarpit!bilver!bill : bill@bilver.UUCP
bill@bilver.uucp (Bill Vermillion) (04/13/91)
In article <1991Apr10.075541.638@kessner.denver.co.us> david@kessner.denver.co.us (David Kessner) writes: >In article <1991Apr9.075828.2135@ibmpcug.co.uk> hdrw@ibmpcug.co.uk (Howard Winter) writes: >>BTW I understand the medium used in DD vs HD disks IS different, >>and that the coercivity (the ease with which magnetism becomes >>permanent) is the variable. I have certainly never been able to >>reformat an HD 3.5" to 1.44 once it has been formatted at 720, >>and I believe that the switching of strength of magnetism used >>is the reason - the weaker HD field cannot overcome the 720. The reason you can't reformat to 1.44 is that the system checks the density of the disk IF IT HAS BEEN PREVIOUSLY WRITTEN UPON. Bulk erase it and it will work just fine. The HD format current requirements will EASILY overwrite anything that DD writes. But you first have to let the machine know that the disk IS blank, and only a bulk eraser can do that. -- Bill Vermillion - UUCP: uunet!tarpit!bilver!bill : bill@bilver.UUCP
marc@skypod.uucp (Marc Fournier) (04/15/91)
In article <1991Apr9.191024.7048@cc.tut.fi> public@cc.tut.fi (PD Software Group) writes: > > >try this (I mean if you still have those disks): Make a hole to DD >disk at the same location than on the HD disk's HD hole is and try >then read the disk on the HD drive. It should be usable again. > > >I disagree with this. Whatever the manufacturers say about the >differences with the media of DD and HD disks (I admit that most >likely there is some differences between DD and HD disks), it is quite >reliable to use 'hand-made-HDs'. A friend of mine has used such disks >for YEARS without problems - nowadays he has 900-1000 hand-made (and >even nameless) DD-HDs > Can someone tell me if this only works with 3.5" disks, or 5.25" also? I've got tons of DS/DD 5.25" disks that I would like to convert to HD if possible. Thanks -- | Marc G. Fournier (416) 250-8589 | Haven't thought of anything | | Toronto, Ontario | real witty to say here! | | uucp: marc@skypod.uucp --------- And probably... | | Bitnet: marc%skypod@ugw.utcs.utoronto.ca | never will! |
pschwart@vms.macc.wisc.edu (Paul Schwartz) (04/16/91)
In article <1991Apr15.054400.2126@skypod.uucp>, marc@skypod.uucp (Marc Fournier) writes... >In article <1991Apr9.191024.7048@cc.tut.fi> public@cc.tut.fi (PD Software Group) writes: >> >> >>try this (I mean if you still have those disks): Make a hole to DD >>disk at the same location than on the HD disk's HD hole is and try >>then read the disk on the HD drive. It should be usable again. >> >> > Can someone tell me if this only works with 3.5" disks, or >5.25" also? I've got tons of DS/DD 5.25" disks that I would like to >convert to HD if possible. > NO WAY! The diff in media between a DD and a HD 5 1/4 disk is mongo-huge. Plus, no extra hole, anyway. - Z - +-----------------------------------------------------------------------------+ | PauL M SchwartZ | There are many causes worth dying for, | | PSCHWART@macc.wisc.edu | but none worth killing for. | | PSCHWART@wiscmacc.BitNet | - Gandhi | +-----------------------------------------------------------------------------+
hdrw@ibmpcug.co.uk (Howard Winter) (04/17/91)
No - you CANNOT reliably use DD disks as HD - especially 5.25". You can certainly format them (there is no physical indication of the disk type, as there is with 3.5") but you will find that the Format program reports about 25% bad sectors. The inner tracks just cannot take the density unless they are made of the correct material - and 360K disks just aren't. Try writing on sandpaper (the rough side!) with a pencil - you'll find that it is possible with fine grades, but the coarser the grit, the less legible the writing. It's pretty much the same with magnetic media. Disks really aren't that expensive - losing data can be priceless! Howard. -- Automatic Disclaimer: The views expressed above are those of the author alone and may not represent the views of the IBM PC User Group. -- hdrw@ibmpcug.Co.UK Howard Winter 0W21' 51N43'
steved@hrshcx.csd.harris.com (Steve Daukas) (04/18/91)
In article <1991Apr15.212942.8780@macc.wisc.edu> pschwart@vms.macc.wisc.edu (Paul Schwartz) writes: >In article <1991Apr15.054400.2126@skypod.uucp>, marc@skypod.uucp (Marc Fournier) writes... > > NO WAY! The diff in media between a DD and a HD 5 1/4 disk is mongo-huge. >Plus, no extra hole, anyway. > - Z - > I have used lots of DD 5.25" disks formatted as HD with no problems (at least not for the last 6 years anyway). Steve -- .-------------------..-------------------------. | Stephen C. Daukas || sdaukas@csd.harris.com | | (617) 221-1834 || uunet!hcx1!misg!sdaukas | `-------------------'`-------------------------'
nigelm@ohm.york.ac.uk (Nigel Metheringham) (04/18/91)
In <1991Apr17.000314.29195@ibmpcug.co.uk> hdrw@ibmpcug.co.uk (Howard Winter) writes: >No - you CANNOT reliably use DD disks as HD - especially 5.25". >You can certainly format them (there is no physical indication >of the disk type, as there is with 3.5") but you will find that >the Format program reports about 25% bad sectors. The inner tracks >just cannot take the density unless they are made of the correct >material - and 360K disks just aren't. This applies just as much to 3.5 inch disks. We have just had a set of people demonstrating software at an exhibition here. One bloke had bought his precious programs with him (only one copy) on some 3.5 inch 720KB disks with the extra hole punched in them to persuade the PC that they were really 1.4MB disks (apparently his Lab had run out of disks in the few days before he came to the exhibition). Our systems could read about 75% of the disk, but wouldn't touch the inner tracks on any of the drives we tried. The morals (probably loose) of the story are:- 1. Use disks of the correct type for the capacity you want. 2. Always have a second copy. 3. If its important have an extra set of copies, or some other way of rebulding it. 4. If its very important don't let it near a computer in the first place :-) ! Nigel. -- # Nigel Metheringham # EMail: nigelm@ohm.york.ac.uk # # System Administrator # Phone: +44 904 432374 # # Department of Electronics # Fax: +44 904 432335 # # University of York, Heslington, York, UK, YO1 5DD #