matt@iquery.UUCP (Matt Reedy) (10/26/89)
I'm confused about quarter-inch cartridge tape drives. I read that there are 40MB, 60MB, 120MB, & 150MB tape drives. I read about "standards" like QIC-24 and QIC-40. I hear that some are SCSI, some aren't. I know about tape cartridges like DC300A, DC300XL/P, DC600A and so on. I hear that some tape drives can read tapes created on other, different capacity drives. I know that sometimes you have to swap bytes when loading tapes made on different drives. And then there's my AT&T 3B2 machine that uses a "streaming" tape that must be formatted before it can be written to. Can someone fill out a table like the following for me to help me understand this quagmire? Many thanks in advance. Tape Drive SCSI or QIC Type of Can read Swap Capacity NOT Standard? Cartridge tapes sized bytes? My real reason for asking is that we want to get a quarter-inch tape drive for a 386 *NIX machine that is as portable as possible (i.e., we'd like to be able to make tapes on this machine that can be read on the widest possible variety of other *NIX machines). matt -- Matthew Reedy UUCP: cs.utexas.edu!swrinde!dpmizar!iquery!matt Programmed Intelligence Corp. 400 N Loop 1604 E, Suite 100 San Antonio, TX 78232 (512) 490 6684 Fax: (512) 490-3590
michaelv@watzman.UUCP (Michael Vishchers) (10/28/89)
From article <169@iquery.UUCP>, by matt@iquery.UUCP (Matt Reedy): > I'm confused about quarter-inch cartridge tape drives. So am I. > Can someone fill out a table like the following for me to help me understand > this quagmire? Many thanks in advance. [deleted] I think this is of interest to many people (me too!). I would like to buy such a drive (with SCSI) for an Atari ST, but it shoould be able to read tapes from SUN workstations etc. Matt, maybe you could collect and edit the answers and post the results in this group ? Michael -- _____________________________________________________________________________ Michael Vishchers (uunet!mcsun!unido!watzman!michaelv) "Wer fuer alles offen ist, kann nicht ganz dicht sein." (unbekannt) _____________________________________________________________________________
witold@cs.washington.edu (Witold Paluszynski) (10/30/89)
In article <169@iquery.UUCP> matt@iquery.UUCP (Matt Reedy) writes: >I'm confused about quarter-inch cartridge tape drives. I read that there are >40MB, 60MB, 120MB, & 150MB tape drives. I read about "standards" like QIC-24 > ... >My real reason for asking is that we want to get a quarter-inch tape drive for >a 386 *NIX machine that is as portable as possible (i.e., we'd like to be able >to make tapes on this machine that can be read on the widest possible variety >of other *NIX machines). Well, there appears to be lots of QIC standards but the answer to this question is simple: they are generally INCOMPATIBLE. I was recently shopping for a quarter inch drive with similar objectives (compatibility with other systems) and I was amazed to discover that 60 MB drives were incompatible with 150 MB drives. Yes, you can read a 60 MB tape in a 150 MB drive, but you can't write it. What I would expect is the sort of upwards compatibility as with 9 track tapes, where even the newest drives can write 800 bpi tapes. I guess the manufacturers have discovered that with that much compatibility people just keep using their old drives instead of replacing them with new ones all the time. So they were careful to prevent this kind of disaster by designing incompatible standards. I hope someone can prove me wrong. Witold
kev@hpcpbla.HP.COM (Kevin Jones) (10/30/89)
What tends to happen with quarter inch tapes is that to get more data onto a tape, successive standards define more tracks on the tape. As the number of tracks on a tape increase, their width decreases (after all, its still 1/4 inch :-) When it comes to writing a track, the WIDTH of the write head which creates the track is (approx) the width of the track. Higher capacity drives therefore have narrower write heads than the older drives (QIC24 -> QIC150 -> QIC320 etc....). This means that it is impossible for a "newer" drive to write "wide tracks" (which the "older" drives can read). It IS possible however for a "newer" drive to READ tapes written with wider tracks since the read head fits "inside" tracks (as written by either drive). It is therefore possible to build a drive which reads/writes a new format but can only read older formats. It is extreemly difficult (read also: expensive) to try and build a drive to read and write all formats. ----------------------------------------------------------------- Kevin Jones. | Hewlett Packard Ltd, | Computer Peripherals Bristol, kev%hpcpbla@hplb.hpl.hp.com | Filton Road, | Stoke Gifford, Tel: 011 44 272 799910 (ext 22351) | Bristol. BS12 6QZ. | ENGLAND. -----------------------------------------------------------------
poole@chx400.switch.ch (Simon Poole) (10/31/89)
In article <9633@june.cs.washington.edu> witold@june.cs.washington.edu (Witold Paluszynski) writes: ..... [complaining that you can't write 60MB cartridges in a 150MB drive] >What I would expect is the sort of upwards compatibility as with >9 track tapes, where even the newest drives can write 800 bpi tapes. You must be joking, to be able to write 800 bpi with a new drive, you generally have to go and buy an expensive trispeed tape. The 800 bpi format is completly incompatible with the one for 1600/6250 bpi. -- ------------------------------------------------------------------------ Simon Poole poole@verw.switch.ch/poole@chx400.switch.ch/mcvax!cernvax!chx400!poole ------------------------------------------------------------------------
witold@cs.washington.edu (Witold Paluszynski) (10/31/89)
In article <1989Oct30.220321.25394@chx400.switch.ch> poole@chx400.switch.ch (Simon Poole) writes: >..... >[complaining that you can't write 60MB cartridges in a 150MB drive] >>What I would expect is the sort of upwards compatibility as with >>9 track tapes, where even the newest drives can write 800 bpi tapes. >You must be joking, to be able to write 800 bpi with a new drive, >you generally have to go and buy an expensive trispeed tape. The 800 >bpi format is completly incompatible with the one for 1600/6250 bpi. Oh, pardon me for not making myself more clear. When I said the 9 track drives were compatible I meant that the COMPATIBLE drives were compatible. Sure you can buy an incompatible drive. But you can also buy a compatible one. No such luck with QIC. Right now these things are new and hot so who would pay any attention. But in a few years the manufacturers will all switch to 150 MB, then to 250 MB, 500 MB, etc., and you will soon be left alone in the cold. Unless you can afford to keep up, throwing away your old drives and buying new ones, thank you. Actually, I don't demand perfect compatibility. 400 bpi drives are gone for good but the time span is so much longer that it is comparable with the lifetime of the drive. The compatibility spans 3 generations, that would be more than enough for QIC. Right now, however, the compatibility is non-existent. Witold
mhw@wittsend.lbp.harris.com (Michael H. Warfield (Mike)) (11/08/89)
In article <9638@june.cs.washington.edu> witold@june.cs.washington.edu (Witold Paluszynski) writes: >Oh, pardon me for not making myself more clear. When I said the >9 track drives were compatible I meant that the COMPATIBLE drives >were compatible. Sure you can buy an incompatible drive. But >you can also buy a compatible one. No such luck with QIC. The example with the 9 track drives though is not a good one. The difference in density was in the frpi (flux reversals per inch). The difference in the QIC formats is in tpi (tracks per inch). The newer format involves a higher track density that effectively doubles the data on the tape (60 Meg tapes record 120Meg). In order to get to 150Meg, different tapes are used that also support a higher frpi as well as tpi. The problem is that the technology, in this case, is not really downward compatible when you change the tpi. To increase the tpi you have to use thinner heads. Now thinner heads can read the wide tracks of the old format just fine. However, if you were to record the old track density with the newer head geometry, you get thinner tracks spaced out with wide gaps between them that have not been erased or recorded on. The thinner tracks result in a MUCH lower signal level on the older heads and the gaps between the tracks introduce noise (or worse extranious unerased data) into the playback system. The result is that the old heads cannot read the thinner tracks. This is a physical limitation resulting from the thinner tracks. The only way around it is not to use the thinner tracks. Which means you don't use this technology. So to get the advantage of THIS technology you sacrifice some compatibility. A closer analogy with the large tapes would not be the difference between 800 bpi and 1600 bpi but rather between 7 track tapes (How old are you? Am I showing MY age :-) :-) ) and 9 track tapes. Yes there were some strange animals that could support both, but only by having two complete head assemblies. Most of the time it was wiser to just keep one old clunker around for the 7 track tapes after upgrading to 9 track tapes. Some places couldn't even justify that after a while and just farmed out their 7 track tapes to outside vendors who specialized in conversions. A comparible situation currently exists in the MS-DOS world. The 1.2Meg 5 1/4" floppy disks are records at 96tpi. The older 360K disk are recorded at 48tpi. It is a simple matter for the 1.2Meg drives to read the 360K format. You can format and record the 360K format on the 1.2 Meg drives but the chances of it being readable on a 360K drive is very slim. In contrast the 3 1/2" floppy drives use a different recording density between the 1.44Meg and the 720K formats. For this reason the 1.44Meg drives are fully capable of reading and writing the 720K disks just by changing the data transfer rate. The resulting disks are identical to a disk recorded on a 720K drive. The difference in the head geometry on the new high capacity tape drives means it is physically incapable of recording a tape that is identical to a tape recorded by an old drive. It is then difficult to expect the old drive to be able to read that tape. The fact that the manufactures do not enable this type of action is purely defensive. I certainly would not want to deal with the volume of customer complaints that would result when the old drives fail miserably trying to read a tape from a new drive. Michael H. Warfield (The Mad Wizard) | gatech.edu!galbp!wittsend!mhw (404) 270-2123 / 270-2098 | mhw@wittsend.LBP.HARRIS.COM An optimist believes we live in the best of all possible worlds. A pessimist is sure of it!