rschmidt@copper.ucs.indiana.edu (roy schmidt) (06/18/91)
Chris Genly writes: > 1) Why can't I format a DS HD diskette as a DS DD disk? > The DS HD diskette uses a different type of medium for recording. It is designed to hold a weaker magnetic "charge" for each bit written so that the data can be written more densely within the same area. This makes it impossible to use a DS DD disk for HD because the magnetic field generated by the head on an HD drive is too weak for the medium. However, there is no good reason why you can't format the HD as DD. I have done this many times, sometimes on 360K drives. > 2) Is there a slot or hole somewhere in the floppy jacket that tells > the drive what capacity disk is inserted? Not on the 5-1/4" disks. The difference in medium is only important for the HD drives, and they can quickly detect a DD disk because they can't read back to verify the first write. Your DD drive should be indifferent to the medium. > > 2) What are the various diskette formats available now, and what > are thier capacities? The popular ones are: 5-1/4" 3-1/2" DS DD 360K 720K DS HD 1.2M 1.44M The old ones are: (all 5-1/4") DS DD 320K SS DD 180K SS DD 160K > >Thanks in advance. > You're welcome, even if you did ask three questions for the price of 2! :-) -- -------------------------------------------------------------------------- Roy Schmidt | #include <disclaimer.h> Indiana University | /* They are _my_ thoughts, and you can't Graduate School of Business | have them, so there! */
ntaib@silver.ucs.indiana.edu (Nur Iskandar Taib) (06/19/91)
>In recent years HD floppies almost never have a hub ring, will DD >always do. In the past this was not true, so it's certainly possible >to find a DD disk without a hub ring. As far as a I know, no drive I remember someone selling a gizmo for putting on hub rings years ago. Incidentally, why don't HD diskettes have hub rings? You'll also notice that HD floppies rotate all the time, DD stop spinning between reads or writes (for 5 1/4s, that is). -- ------------------------------------------------------------------------------- Iskandar Taib | The only thing worse than Peach ala Internet: NTAIB@AQUA.UCS.INDIANA.EDU | Frog is Frog ala Peach Bitnet: NTAIB@IUBACS ! -------------------------------------------------------------------------------
anthony@convex.csd.uwm.edu (Anthony J Stieber) (06/30/91)
In article <1991Jun28.220658.23540@eagle.lerc.nasa.gov> afdenis@lims05.lerc.nasa.gov writes: >In article <13264@uwm.edu>, anthony@convex.csd.uwm.edu (Anthony J Stieber) writes... >>In article <1991Jun18.234702.9028@bronze.ucs.indiana.edu> ntaib@silver.ucs.indiana.edu (Nur Iskandar Taib) writes: >>>Incidentally, why don't HD diskettes have hub >>>rings? You'll also notice that HD floppies >> >>I don't really know, I remember reading about how HD drives don't >>need them. It seemed to me that hub rings are there to protect >>the hub from dammage, perhaps someone out there knows the real reason? >> >One possible explanation I heard is that HD disketts have their magnetic >media impregnated to thicker mylar disks for stability. The reasoning was >that the hubrings "thicken" the DS DD disks for positive clamping, and the >HD disks, being thicker initially, don't require them. > >Could be BS but it made sense to me. Well, I got out a micrometer and measured the thickness of some floppies. The 5.24" DSDD, 5.25" DSHD and 3.5" DSDD disks I tested all measured 0.003 inches in thickness. Oddly enough, the MEI/Micro Center catalog has listed the HD disks as being 0.005 inches in thickness while DD as only 0.0003 (within spec). I'll check around on other HD disks and see what I find. Thickness is not given in the specs for either of the 3.5" disks. The hub ring on the 5.25" DD disk was 0.008 inches thick. I don't know what this means, maybe the cheap 5.25" disks are cheap because they are thin, maybe not. There are other HD disks I can check out later. By the way, here are the coercivity specs that started this whole thing. size density oersteds ------------------------ 5.25" DD 320 5.25" HD 640 3.5" DD 600 3.5" HD 720 Higher coercivity corresponds to higher write currents in the read/write heads on the disk drive. HD disks in a DD drive don't work well because the high coercivity medium actually resists being written to by the low write current head. And some definitions: co-er-civ-i-ty \,ko^--,er-'siv-et-e^-\ n (1898) :the property of a material determined by the value of the coercive force when the material has been magnetized to saturation oer-sted \'er-sted\ n [Hans Christian Oersted] (ca. 1889) :the centimeter-gram-second electromagnetic unit of magnetic intensity equal to the intensity of a magnetic field in a vacuum in which a unit magnetic pole experiences a mechanical force of one dyne in the direction of the field -- <-:(= Anthony Stieber anthony@csd4.csd.uwm.edu uwm!uwmcsd4!anthony Psion Mailing List subscriber submissions psion ----------\ the (human) moderator psion-owner -------+--@csd4.csd.uwm.edu subscriptions and file requests psion-request ----/