Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uflorida!mlb.semi.harris.com!thrush.mlb.semi.harris.com!del From: del@thrush.mlb.semi.harris.com (Don Lewis) Newsgroups: comp.periphs.scsi Subject: Re: QIC-150 <-> QIC-24 Message-ID: <1990Aug18.002947.4814@mlb.semi.harris.com> Date: 18 Aug 90 00:29:47 GMT References: <224@rusux1.rus.uni-stuttgart.de> Sender: news@mlb.semi.harris.com Organization: Harris Semiconductor, Melbourne FL Lines: 48 In article <224@rusux1.rus.uni-stuttgart.de> wschmidt%phobix@apatix.caed.IAO.FhG.de (Wolfram Schmidt) writes: >Recently i read in a Sun manual that QIC-150 drives aren't able to write >QIC-24 format. >man st(4S) says there is an error message: wrong media for writing if you >try to write on a DC-300XL-type tape. Only DC-6150 blah blah blah ... >These are 600 foot long (as of my knowledge) and good for 150 MB. >I wrote on a DC-600 tape with this drive. Since DC-600 are 600 fott length >too, the material must be different. Why does the drive write to this tape? >Data may be lost sooner or later. Drive was Archive Viper (?). It looks to me like the material is the same. Both DC-600 and DC-6150 tapes are labelled 12500 ftpi. After doing some experimentation with both tape types on a QIC-150 drive, I found that I could write about 155 MB to a DC-6150 tape and about 130 MB on a DC-600 tape. I got about the same (small) number of retries on both. Supposedly there is a QIC-120 format which allows 125 MB on a tape. The difference between the two formats is supposedly that the QIC-150 format puts 18 tracks on the tape and the QIC-120 format puts 15 tracks on the tape. If we assume that the linear bit density is the same for both formats, then the ratio between the capacities appears to be the same as the ratio of the numbers of tracks. My guess is that the DC-6150 media is manufactured in such a way that data may be written closer to the edges of the tape than it can with DC-600 tape and that the drive senses the media type by measuring the distance between the BOT holes and figures out how many tracks it is allowed to write. Disclaimer: I have not seen any official word that existing QIC-150 drives can write QIC-120 format or write anything on DC-600 tape. > >The main point of this posting is: are there any QIC-150 drives that are >capable of writing QIC-24 format (on DC-6150 or DC600 cartridges)? >I need such a beast. I don't think there is such a thing. Since QIC-150 format has more data tracks (18) across the width of the 1/4 inch of tape than QIC-24 format does (9), the QIC-150 tracks must be narrower. This means that the tape head in a QIC-150 drive is not capable writing the wide tracks that a QIC-24 drive would need in order to successfully read the data. There should not be a problem with the tape head in a QIC-150 drive reading the wide data tracks on a QIC-24 format tape. I suppose that it would be possible to build a tape drive with two different heads or a head that can write both widths, but I have not heard of anything like this. -- Don "Truck" Lewis Harris Semiconductor Internet: del@mlb.semi.harris.com PO Box 883 MS 62A-028 Phone: (407) 729-5205 Melbourne, FL 32901