Newsgroups: comp.sys.dec.micro Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!cunixf.cc.columbia.edu!shibuya.cc.columbia.edu!lasner From: lasner@shibuya.cc.columbia.edu (Charles Lasner) Subject: Re: Rainbow EchoMail Digest Message-ID: <1991Apr21.191505.17129@cunixf.cc.columbia.edu> Summary: RX-50s, the naked truth Keywords: RX50,hub-rings Sender: Charles Lasner Nntp-Posting-Host: shibuya.cc.columbia.edu Reply-To: lasner@shibuya.cc.columbia.edu (Charles Lasner) Organization: Columbia University References: Date: Sun, 21 Apr 1991 19:15:05 GMT Re: the never-ending RX50 media story. I was the one quoted here again, so I'll reply about the Maxell diskettes. Anytime you use hub-ringed diskettes in a 96 tpi drive, you are taking a high-risk chance with your data. The condition of the drive (dirt, age) as well as the condition of the diskette, as well as its manufacture, dictate your (slim) chances of long-term reliability of the data. The problem is that those diskettes were designed to deal with the problems of the widespread DD-type drives used on a million poor xt clones. Many of these crappy drives chew up the hub areas of the diskettes. Any of you out there remember what RX01s do to the 8" diskettes? Any of you remember the third-party add-on user-installable hub-rings? The 48 TPI 40 track drives used with those DD disks have "non-thin-film" heads, to coin a retroactive phrase. This means that each track, which owns 1/48 " uses about 50% of this space for data recording. The rest is guard zone and tunnel erase zone. This is also why you can read the DD disks in the HD drives so easily; basically you can't miss :-) The 96 TPI disks, like the RX50, use thin-film heads. Not as snazzy as the HD disk drives like TEAC FD-55GFR, as used in good AT-clones, but 96 TPI none the less. This of course means that each track owns 1/2 of what the corresponding track owns in the 48 TPI drive, but it doesn't end there. The thin-film heads use a shorter magnetic gap, which translates into far less use of the media than would otherwise be predicted, about 1/5 as much. So, this means that 96 TPI drives record their data on about 1/10 of the media as do 48 TPI drives. The chances that the media's hub-rings can be grabbed differently each time now greatly increases chances of data errors. Each time the diskette is passed through a hub-chewing drive, the greater the likelihood that a 96 TPI drive can't reliably use that diskette. Further, some vendors, possibly Maxell, will use somewhat thicker hubrings, in an attempt to produce better results with the intended use on DD drives, which only worsens prospects for use on 96 TPI drives. I myself have had problems using 3M diskettes intended for DD usage. The DSDD media were formatted on HD 96 TPI drives in DD format for possible reading on DD drives (360K). They were unreliable on other HD drives due to the slight wear on the hub-rings. Registration errors were high because the HD drive couldn't reliably grab the media in the same place. We resorted to pulling the media out and reseating it a lot to retrieve the data with many retries. If the same media were reformatted on the target drive, and not removed and reseated, it read back fine. Removing and reseating the diskette made it flakey even on the drive that formatted and wrote it moments ago. These same diskettes worked fine on TEAC FD55B drives (DD 360K), because the hub-rings are not really that worn, just beyond the tolerance limit for 96 TPI mis-use. cjl (Charles Lasner) (lasner@watsun.cc.columbia.edu)