Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ames!sun-barr!apple!vsi1!octopus!pete From: pete@Octopus.COM (Pete Holzmann) Newsgroups: comp.sys.ibm.pc Subject: Re: 3.5" High-Density Woes Summary: Leave 5.25" disks out of the diskussion (:-)) please Keywords: penny wise, pound foolish Message-ID: <1989Aug23.151302.2622@Octopus.COM> Date: 23 Aug 89 15:13:02 GMT References: <1001@apctrc.UUCP> <5221@mtuxo.att.com> Reply-To: pete@octopus.UUCP (Pete Holzmann) Distribution: usa Organization: Octopus Enterprises, Cupertino CA Lines: 95 In article <5221@mtuxo.att.com> gjp1@mtuxo.UUCP (XMRK4-G.PATEMAN) writes: >(George E. Lehmann) writes: >>DON'T USE 3.5" DS/DD DISKETTES FOR HD (1.44MB) USAGE!!!!! > >AND DON'T USE 5.25" DS/DD DISKETTES FOR HD (1.2MB) USAGE!!!! > >OK, once more for those who still believe it's a cost-effective approach: Let's pause for breath here, please. It is fully proven that 360K floppies are not reliable when written in a 1.2M drive. Not even at 360K, let alone at 1.2M. I have never, ever, seen a 360K floppy formatted at 1.2M come even *close* to getting the full 1.2M available, and I've personally done extensive testing to verify that a 360K diskette written (at 360K density) on a 1.2M drive is simply not *always* going to be readable on another drive. It works much of the time, but not always. But 3.5" drives are a completely different matter. There is far more compatibility! A 1.44M drive can reliably read and write the correct disk at the correct density. There is no question of that. There's absolutely no need to buy both a 1.44 and a 720K drive. In addition, whenever a 720K floppy is formatted at 1.44M, you don't just get a little more than 720K out of it, you get the whole 1.44M, or very close to it (same as you do when formatting a "real" 1.44M diskette). So the real-world situation as we see it so far is: 5.25" disks: no *reliable* compatibility between 360K and 1.2M-- o Never get full 1.2M when formatting a 360K at 1.2 o 360K diskettes written on a 1.2 in any mode (360 or 1.2) are not guaranteed to be readable on other drives 3.5" disks: complete compatibility in the short view (what we've seen so far: o Almost always get full 1.44 when formatting 720 at 1.44 o 720K diskettes written on a 1.44 drive are always readable when written at 720K, and the majority of responses I've seen so far indicate that they are readable when written at 1.44M. So. Please let's limit the discussion to the remaining unknown, which can be verified by experiment (manufacturer's experiment is fine with me, but perhaps different diskette manufacturers have different quality diskettes!) The only unknown about 720-on-1.44 is: - What is the reliability of a 720K diskette formatted at 1.44M? I would personally love to see postings from people who have experience with this setup. We've heard from a few people who've just started down that road, and are very positive. How about people who've done it longer than a month or two? Please, postings like the following only confuse the issue: >When you format a low density (LD) disk in a high density (HD) drive, >a large number of sectors will be marked as "bad". They're not actually >bad, of course. It's just that the 300 Oersted magnetic coating of an LD >disk can't hold the signal the same way an HD's 600 Oe coating can. Look >at the two types side-by-side. The HD disk has a noticeably darker coating. [The last sentence is true. But the first one is demonstrably false. Does this guy really talk from experience, or from theory?] >Alright, so you've formatted the 360K at 1.2M and all the "bad" sectors have >been marked. You don't quite have 1.2M but you have a lot more than 360K. >The problem is that many of the marginal sectors which read back successfully >THIS TIME won't necessarily be readable later on when the disk contains your >valuable data. How likely is that, you ask? VERY! An associate of mine >used LDs exclusively on his HD machine and found that more than half of them >contained unreadable files. When he tried to read them on another machine, >the situation was even worse. [If this 'associate' was working in the 5.25" world, of COURSE he had trouble. 360K and 1.2M diskettes simply don't mix reliable on the same drive at all. That has nothing at all to do with 3.5" drives...] I'm sorry this turned into such a long posting, especially since I really have little knowledge to add to the discussion. I've only started using 720K in 1.44M drives recently myself, and don't have time to do my usual experiments- to-find-the-real-answer. [Somebody ought to get a box of each of several brands of 720K disks, do an archival backup on each box at 1.44M, then report on the readability of the disks over the next year (or more!)...] Pete -- Peter Holzmann, Octopus Enterprises |(if you're a techie Christian & are 19611 La Mar Ct., Cupertino, CA 95014 |interested in helping w/ the Great UUCP: {hpda,pyramid}!octopus!pete |Commission, email dsa-contact@octopus) DSA office ans mach=408/996-7746;Work (SLP) voice=408/985-7400,FAX=408/985-0859