vu0112@bingvaxu.cc.binghamton.edu (Cliff Joslyn) (06/19/89)
I'm beginning to doubt common sense about diskette densities. Both single and double sided diskettes can be formatted as if they were double. I'm told it's simply a difference in quality control. On my new 1.2 meg 5.25" drive I can format DS/DD disks at 1.2 meg? What am I risking by not buying HD disks? etc. -- O----------------------------------------------------------------------> | Cliff Joslyn, Cybernetician at Large | Systems Science, SUNY Binghamton, vu0112@bingvaxu.cc.binghamton.edu V All the world is biscuit shaped. . .
conan@vax1.acs.udel.EDU (Robert B Carroll) (06/19/89)
In article <2210@bingvaxu.cc.binghamton.edu> vu0112@bingvaxu.cc.binghamton.edu (Cliff Joslyn) writes: >on my 1.2 meg 5.25" drive I can format DS/DD disks at 1.2 meg? What am I >risking by not buying HD disks? etc. i doubt it very much. lots of bad sectors. you might be able to get away with 800K or so(and a bunch of bad sectors), but i'd question the reliability later. people always 'used' to do the cut a new write protect tab on single sided disks. -- conan@vax1.acs.udel.edu OR conan@192.5.57.1 CONAN THE BARBARIAN of Cimmeria
brown@astroatc.UUCP (Vidiot) (06/19/89)
In article <2210@bingvaxu.cc.binghamton.edu> vu0112@bingvaxu.cc.binghamton.edu (Cliff Joslyn) writes:
<
<I'm beginning to doubt common sense about diskette densities. Both
<single and double sided diskettes can be formatted as if they were
<double. I'm told it's simply a difference in quality control. On my
<new 1.2 meg 5.25" drive I can format DS/DD disks at 1.2 meg? What am I
<risking by not buying HD disks? etc.
You are risking loss of data, because the regular diskettes will not format
under the 1.2 meg writing currents. You will have many bad sectors and who
knows how many will be marginal. Once a diskette (that is not HD) is formatted
that way, they normally will not format the correct way. I have done it.
The diskette had to be thrown away.
--
harvard\ att!nicmad\
Vidiot ucbvax!uwvax..........!astroatc!brown
rutgers/ decvax!nicmad/
ARPA/INTERNET: brown%astroatc.UUCP@spool.cs.wisc.edumbb@cbnewsh.ATT.COM (martin.b.brilliant) (06/19/89)
From article <2210@bingvaxu.cc.binghamton.edu>, by vu0112@bingvaxu.cc.binghamton.edu (Cliff Joslyn): > > I'm beginning to doubt common sense about diskette densities. Both > single and double sided diskettes can be formatted as if they were > double. I'm told it's simply a difference in quality control. On my > new 1.2 meg 5.25" drive I can format DS/DD disks at 1.2 meg? What am I > risking by not buying HD disks? etc. You'll be happy to know I can't do that. I have a 1.2 meg drive with suitable controller in an XT clone, and I have both kinds of disks. When I format an HD-labeled disk at 1.2 meg it comes up just fine. If I put in a 360K-labeled disk and enter exactly the same command line, I get a gradually increasing series of horrendous grunches, grinds, and groans, and I eventually chicken out and abort. Of course, I can format the 360K disks with the /4 flag, and they quietly come up 360K. M. B. Brilliant Marty AT&T-BL HO 3D-520 (201) 949-1858 Holmdel, NJ 07733 att!hounx!marty1 or marty1@hounx.ATT.COM Disclaimer: Opinions stated herein are mine unless and until my employer explicitly claims them; then I lose all rights to them.
hollen@zeta.megatek.uucp (Dion Hollenbeck) (06/20/89)
From article <2210@bingvaxu.cc.binghamton.edu>, by vu0112@bingvaxu.cc.binghamton.edu (Cliff Joslyn): > > I'm beginning to doubt common sense about diskette densities. Both > single and double sided diskettes can be formatted as if they were > double. I'm told it's simply a difference in quality control. On my > new 1.2 meg 5.25" drive I can format DS/DD disks at 1.2 meg? What am I > risking by not buying HD disks? etc. You didn't ask this, but it may help someone. DSDD disks can be formatted for up to 800k. This is an unusual configuration because it uses 10 sectors per track which the UCSD p-System does reliably, but I never figured out why MS-DOS only used a max of 9 per track. The format using 9 sectors per track is 80 tracks of 8 sectors for a total of 720k. You merely need to tell DOS via DRIVPARM or by using DRIVER.SYS that you have a 720k 3 1/2" drive and it will not know that you really have a 720k 5 1/4". BTW, you must have the correct disk drive (like a Shugart 465). A standard 360k drive will NOT make or read 720k disks and a 720k driver will not make or read 360k disks. FASTBACK PLUS can be configured to recognize these drives as 720k drives and works perfectly. In fact, this is the use I have put them to. Dion Hollenbeck (619) 455-5590 x2814 Megatek Corporation, 9645 Scranton Road, San Diego, CA 92121 seismo!s3sun!megatek!hollen ames!scubed/
bobc@killer.DALLAS.TX.US (Bob Calbridge) (06/22/89)
In article <586@megatek.UUCP>, hollen@zeta.megatek.uucp (Dion Hollenbeck) writes:
+ From article <2210@bingvaxu.cc.binghamton.edu>, by vu0112@bingvaxu.cc.binghamton.edu (Cliff Joslyn):
+ >
+ > I'm beginning to doubt common sense about diskette densities. Both
+ > single and double sided diskettes can be formatted as if they were
+ > double. I'm told it's simply a difference in quality control. On my
+ > new 1.2 meg 5.25" drive I can format DS/DD disks at 1.2 meg? What am I
+ > risking by not buying HD disks? etc.
+
+
+ You didn't ask this, but it may help someone. DSDD disks can be
+ formatted for up to 800k. This is an unusual configuration because
+ it uses 10 sectors per track which the UCSD p-System does reliably,
+ but I never figured out why MS-DOS only used a max of 9 per track.
+ The format using 9 sectors per track is 80 tracks of 8 sectors for
+ a total of 720k. You merely need to tell DOS via DRIVPARM or by
+ using DRIVER.SYS that you have a 720k 3 1/2" drive and it will not
+ know that you really have a 720k 5 1/4". BTW, you must have the
+ correct disk drive (like a Shugart 465). A standard 360k drive will
+ NOT make or read 720k disks and a 720k driver will not make or read
+ 360k disks. FASTBACK PLUS can be configured to recognize these
+ drives as 720k drives and works perfectly. In fact, this is the
+ use I have put them to.
Along a similar line I forgetfully forgot the /4 switch with a 360K diskette
in the drive. The program dutifully formatted the diskette. However, I
showed a bit more than 720K on the disk and a rather large number of bad
sectors to make up the remaining 1.2M. I went ahead and copied a large
number of files onto the diskette and it copied okay. Reading the disk
presented no problem and copying from it worked fine.
However, I'm not going trust this to keep my important files on.
--
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
= I know it's petty.......... =
- But I have to justify my salary! -
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=las) (06/24/89)
In article <8428@killer.DALLAS.TX.US> bobc@killer.DALLAS.TX.US (Bob Calbridge) writes: >In article <586@megatek.UUCP>, hollen@zeta.megatek.uucp (Dion Hollenbeck) writes: >+ From article <2210@bingvaxu.cc.binghamton.edu>, by vu0112@bingvaxu.cc.binghamton.edu (Cliff Joslyn): >+ You didn't ask this, but it may help someone. DSDD disks can be >+ formatted for up to 800k. This is an unusual configuration because >+ it uses 10 sectors per track which the UCSD p-System does reliably, >+ but I never figured out why MS-DOS only used a max of 9 per track. In order to make room for 10 sectors per track on 5 1/4 inch floppy disks, you must reduce the gap between sectors to a value less than the "standard" originally defined by IBM (let's see... I think they called it 3740, yeah that sounds about right) for floppy disks. Of course, that standard was very conservative, having been tailored to the capabilities of their very early tech 8 inch floppies (called - surprise, surprise - the 3740). Advances in the state of the art had long since reduced the need for such conservative specs when IBM decided to go from 8 to 9 sectors per track on the PC, but apparently the old spec was too much of a barrier to cross. It is, after all, an IBM standard. It took a non- IBM maverick company to go to 10 sectors per track, but the P-System was never really in the PC mainstream and it didn't have much of an affect on the DOS mainstream. regards, Larry -- Signed: Larry A. Shurr (cbema!las@att.ATT.COM or att!cbema!las) Clever signature, Wonderful wit, Outdo the others, Be a big hit! - Burma Shave (With apologies to the real thing. The above represents my views only.) (Please note my mailing address. Mail sent directly to cbnews doesn't make it.)
chasm@killer.DALLAS.TX.US (Charles Marslett) (06/26/89)
In article <7710@cbnews.ATT.COM>, cbema!las@cbnews.ATT.COM (cbema!las) writes: > In article <8428@killer.DALLAS.TX.US> bobc@killer.DALLAS.TX.US (Bob Calbridge) writes: > >In article <586@megatek.UUCP>, hollen@zeta.megatek.uucp (Dion Hollenbeck) writes: > >+ From article <2210@bingvaxu.cc.binghamton.edu>, by vu0112@bingvaxu.cc.binghamton.edu (Cliff Joslyn): > > >+ You didn't ask this, but it may help someone. DSDD disks can be > >+ formatted for up to 800k. This is an unusual configuration because > >+ it uses 10 sectors per track which the UCSD p-System does reliably, > >+ but I never figured out why MS-DOS only used a max of 9 per track. I have had quite a bit of experience mailing diskettes, moving code from one machine to another, etc, with 9 and 10 sector/track diskettes. And the 9 sector/track format works going from ATs to XTs, from Fujitsu drives to Teac to Cannon to ... On the other hand, 10 sector/track diskettes are readable at the destination (usually), but the first time the dummy who received the diskette tries to write anything to it - BOOM goes the FAT, and nothing is accessable on the disk ever again! (Appologies to anyone who has written a memo on a master disk -- I have done it, too ;^) The problem is that there is still some variation between drives (even drives made the same year by the same company), and there is no room at all for any speed deviation in the 10 sector/track format. On the other hand, if you have reasonably well maintained drives and they are no more than, say, two years old, you can probably use 10 sectors/track reliably. For backups, I reccommend you live with 9 or go to 15 (A 1.2 MB diskette, that is to say -- they are not really very expensive, I pay $.50 each, and they are certainly worth that! [5 1/4s, 3 1/2s are still a bit more expensive]. > In order to make room for 10 sectors per track on 5 1/4 inch floppy > disks, you must reduce the gap between sectors to a value less than > the "standard" originally defined by IBM (let's see... I think they > called it 3740, yeah that sounds about right) for floppy disks. Of > course, that standard was very conservative, having been tailored to > the capabilities of their very early tech 8 inch floppies (called - > surprise, surprise - the 3740). The original gap was 42 bytes (out of about 330) for 8" media, for 5 1/4" media it was increased to 48 bytes (the drive power supplies and moters were not so reliable), and to add a tenth sector it has to be set to around 15 or so. Since the floppy data seperator requires 10 bytes or so, this leaves very little room for speed variation (5 bytes out of 300 is less than 2%). > Advances in the state of the art had long since reduced the need for > such conservative specs when IBM decided to go from 8 to 9 sectors > per track on the PC, but apparently the old spec was too much of a > barrier to cross. It is, after all, an IBM standard. It took a non- > IBM maverick company to go to 10 sectors per track, but the P-System > was never really in the PC mainstream and it didn't have much of an > affect on the DOS mainstream. IBM did not change anything when they went from 8 to 9 sectors/track, since the difference was a performance and simplicity loss on one side in exchange for a capacity gain on the other (old drives stepped very slowly, and with essentially an unused sector at the end of each track the drive had time to step to the next track before its first sector came under the read/write head. Today we use skewed formatting if we need that kind of tweaking, and we still get the capacity. The format routine is just a bit more complex. It had no effect on the DOS mainstream, mostly because it would never have been accepted by software vendors, so anyone who used it would have to support two formats (read, more work, no more pay, never get done ;^). No major vendor thought it worth the effort. > regards, Larry > -- > Signed: Larry A. Shurr (cbema!las@att.ATT.COM or att!cbema!las) > Clever signature, Wonderful wit, Outdo the others, Be a big hit! - Burma Shave > (With apologies to the real thing. The above represents my views only.) > (Please note my mailing address. Mail sent directly to cbnews doesn't make it.) =========================================================================== Charles Marslett STB Systems, Inc. <== Apply all standard disclaimers Wordmark Systems <== No disclaimers required -- that's just me chasm@killer.dallas.tx.us
fisher@sc2a.unige.ch (Markus Fischer) (06/26/89)
In article <2210@bingvaxu.cc.binghamton.edu>, vu0112@bingvaxu.cc.binghamton.edu (Cliff Joslyn) writes: > I'm beginning to doubt common sense about diskette densities. Both > single and double sided diskettes can be formatted as if they were > double. I'm told it's simply a difference in quality control. On my > new 1.2 meg 5.25" drive I can format DS/DD disks at 1.2 meg? What am I > risking by not buying HD disks? etc. Well, i expored the same topic with the first AT i had access to. The most visual approach is to use Norton's Utilities, whith the `map disk usage' command. As it appeares, the magnetic response of DSDD diskettes is high enough for the EXTERNAL CYLINDERS to be formatted as DSHD. But, as the rotation speed of the drive is constant (i actually heard say of a variable speed drive, i.e. more sectors on the outside... !), the density gets below tolerance in the inside cylinders, thus failing format's own tests and being marked as bad. When you look at the results with a `disk-map' utility, you will see that the limit between `good' and `bad' is a statistical one. Personally, i wouldn't trust the lone good cluster in the middle of bad ones! You must be warned about something else: The heads of a 1.2 Mb drive are smaller than those of a 360 kb. This means that when you modify information stored on a DD (360) diskette using a 1.2 Mb drive, you don't update the entire track ! This means that you might be unable to read the modified diskette on your old 360-drive. The only solution is then to format an unused DD diskette whith the /4 option and to use `diskcopy' or `xcopy'. (Then there is only the small track, no old parasites) So my answer to your original question is: if you follow the manuals, you won't risk (more than usually) to loose data. And if you use the right kind of diskette for your drives (i.e. no DD diskettes in 1.2 Mb drives, even with the /4 option), you won't loose time (i.e. arriving to a site with unreadable data...) Markus Fischer -|--|--|--|--|--|--I Department of Anthropology -|--|--|--|--|--|--|-(#)-I University of Geneva -|--|--|--|--|--|--|--|--|-(#)-|-(#)(#)(_)-I CH-1227 Carouge (GE) -&-(_)-|--|--|-(#)-&--|-(#)(#)(_)(#)-&-(_)(#)-I Switzerland -|--|--|--|--|-(#)(_)-|-(_)(_)(_)(#)-I black (#) to kill ! --|--|-(#)(_)(_)(_)(#)(#)(_)(_) fisher@sc2a.unige.ch =+==+==+==+==+==+==+==+==+==+==+==+==+==+==+=(#)=+ fisher@cgeuge52.bitnet
shapiro@rb-dc1.UUCP (Mike Shapiro) (06/26/89)
In article <2096@astroatc.UUCP> brown@astroatc.UUCP (Vidiot) writes: ... [regarding a question on formatting DSDD diskettes as HD] > > Once a diskette (that is not HD) is formatted >that way, they normally will not format the correct way. I have done it. >The diskette had to be thrown away. I have found that most times when I have had a diskette that was badly messed up in the formatting process, I could simply "bulk erase" it (with a bulk eraser designed for audio or video tape) and start over fresh. I've had very few diskettes that have gone bad, except by excessive wear or mechanical damage, that couldn't be made reusable in this way (even in CP/M days on my Kaypro II.) -- Michael Shapiro, Encore Computer Corporation (formerly Gould/GSD) 15378 Avenue of Science, San Diego, CA 92128 (619)485-0910 UUCP: shapiro@rb-dc1 (This location will close, starting July 10. I will be moving on.)
Ralf.Brown@B.GP.CS.CMU.EDU (06/27/89)
In article <8465@killer.DALLAS.TX.US>, chasm@killer.DALLAS.TX.US (Charles Marslett) writes: }I have had quite a bit of experience mailing diskettes, moving code from }one machine to another, etc, with 9 and 10 sector/track diskettes. And }the 9 sector/track format works going from ATs to XTs, from Fujitsu drives }to Teac to Cannon to ... On the other hand, 10 sector/track diskettes are }readable at the destination (usually), but the first time the dummy who }received the diskette tries to write anything to it - BOOM goes the FAT, }and nothing is accessable on the disk ever again! } }In article <7710@cbnews.ATT.COM>, cbema!las@cbnews.ATT.COM (cbema!las) writes: }> In order to make room for 10 sectors per track on 5 1/4 inch floppy }> disks, you must reduce the gap between sectors to a value less than }> the "standard" originally defined by IBM (let's see... I think they } }The original gap was 42 bytes (out of about 330) for 8" media, for 5 1/4" }media it was increased to 48 bytes (the drive power supplies and moters }were not so reliable), and to add a tenth sector it has to be set to }around 15 or so. Since the floppy data seperator requires 10 bytes or The standard gap for 8- and 9-sector formats is 42 bytes. I believe JFORMAT uses a gap of about 25 bytes (it's been a few years since I had my hands on a copy) for 10-sector disks. }IBM did not change anything when they went from 8 to 9 sectors/track, }since the difference was a performance and simplicity loss on one side }in exchange for a capacity gain on the other (old drives stepped very }[...] } }It [10-sector format] had no effect on the DOS mainstream, mostly because }it would never have }been accepted by software vendors, so anyone who used it would have to }support two formats (read, more work, no more pay, never get done ;^). }No major vendor thought it worth the effort. Then there was the Eagle PC, whose version of MSDOS 1.25 supported 400K disks using 5 1024-byte sectors per track (and a 79-byte gap). IO.SYS used a nice table-driven approach to disk formats, which let me patch the (for me unused) entry for 800K disks (like 400K but 80 tracks) to read and write 360K disks without subdirectories. That particular version of DOS what ahead of its time in other ways, too, including support for 10M and 20M hard disks and a SYSINFO.SYS file specifying the default printer, fast/slow scroll, block/underline cursor, etc. -- UUCP: {ucbvax,harvard}!cs.cmu.edu!ralf -=-=-=- Voice: (412) 268-3053 (school) ARPA: ralf@cs.cmu.edu BIT: ralf%cs.cmu.edu@CMUCCVMA FIDO: Ralf Brown 1:129/46 Disclaimer? I claimed something? "When things start going your way, it's usually because you stopped going the wrong way down a one-way street."