Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!wuarchive!brutus.cs.uiuc.edu!uakari.primate.wisc.edu!caesar.cs.montana.edu!blake!phaedrus From: phaedrus@blake.acs.washington.edu (the Wanderer) Newsgroups: comp.sys.mac.hardware Subject: Re: HD disks in a low density drive Message-ID: <4658@blake.acs.washington.edu> Date: 28 Nov 89 08:25:24 GMT References: Reply-To: phaedrus@blake.acs.washington.edu (the Wanderer) Distribution: comp Organization: University of Washington, Seattle Lines: 38 In article vturner@dante.nmsu.EDU (Vaughan Turner) writes: >I heard somewhere that High Density Mac Disks shouldn't be used on a >low density drive (400 or 800K). I kindof understand why this might >be, but I was wondering if anyone could point me towards some >technical information that confirms this (or not, I'd just like to >know which it is). > >Any help would be appreciated, > Well, there are two reasons that I know/have heard of for not using HD disks in a normal drive (aside from the obvious one of wasting money... :) ). 1) I've talked to several people who theoretically know a lot about such things, and they say that the magnetic coating on the HD disks is not designed for the level/type of current that drives use in writing to the lower-density formats, and that more frequent I/O errors result. I've never run into this personally, but it's something you might want to consider if you're storing critical data. 2) Let's say you ignore 1), and initialize a high-density disk with a 400/800K format in a 400/800K drive. You then try to use said disk in a FDHD (high-density) drive. The Apple FDHD will steadfastly refuse to admit the possibility that an HD disk could conceivably be formatted in anything other than the HD format, and the Mac will give you the infamous "This disk is unreadable" dialog, even though the disk is fine. There is a way around this: just put a strip of dark tape over the square hole at the top-left corner of the HD disk. Of course, beware the usual hazards of tape getting stuck in your drive and disks getting stuck and other such catastrophes. >Vaughan >-- >Vaughan Turner BITNET: mcswvt@nmsuvm1.bitnet >Box 3AT Computer Center INTERNET: vturner@nmsu.edu >Las Cruces, NM 88001 -- Internet: phaedrus@u.washington.edu (University of Washington, Seattle) The views expressed here are not those of this station or its management. "If you can keep your head while those about you are losing theirs, consider an exciting career as a guillotine operator!"