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From: dar@belltec.UUCP (Dimitri Rotow)
Newsgroups: comp.periphs,comp.unix.microport
Subject: Re: tape streamers question
Summary: QIC-36 vs QIC-02
Message-ID: <314@belltec.UUCP>
Date: 23 Dec 88 02:17:09 GMT
References: <1516@bebux.UUCP> <895@starfish.Convergent.COM>
Organization: Bell Technologies, Fremont, CA
Lines: 47

In article <895@starfish.Convergent.COM>, cdold@starfish.Convergent.COM (Clarence Dold) writes:
> From article <1516@bebux.UUCP>, by henk@bebux.UUCP (Henk Dijkstra):
> > I would like to purchase a tape-streamer however one of my wishes is
> > that it is compatible with "frequently" used tape-streamers on UNIX systems.
> > From what I hear that means I have to buy a "QIC-24" format compatible
> 

One of the points Clarence makes needs clarification.  There are two tape
interface standards commonly used between PC boards and tape mechanisms.  The
QIC-36 interface is really a command interface whereas the QIC-02 interface
is more of a bus adaptor spec.  That's why QIC-36 cards are typically "long"
format cards, because they contain the formatter/command electronics, while
QIC-02 cards (being mere bus adaptors) tend to be short cards.  

Almost all streamers use the QIC-36 command interface.  The original QIC-36
card was designed by Northern Telecom and put into mass production by Everex
in their EV series.  Since then, numerous third parties (Wangtek, etc) are
building "PC36" compatible streamer tape controllers.  The tape software
most vendors use will work with all such cards (keeping in mind that any
given driver is always vulnerable to changes in ROMs, PALS, and other
individual design changes).

In recent years tape electronics have advanced to the point that much of the
formatting/command electronics can be integrated onto the tape mechanism's 
own circuit board.  Thus the QIC-36 command interface can be buried inside
the tape unit itself, allowing it to communicate to the host system via a
QIC-02 bus adaptor.   In a correctly implemented QIC-02/Tape system, the
board/drive will look exactly the same to the device driver.  Thus only 
one set of Bell Tech drivers is used for all Bell Tech tape devices, 
regardless of their size or whether the particular adaptor card plugged
into the AT is a QIC-36 unit or a QIC-02.  Again, keep in mind that any 
particular installation is vulnerable to version skew.  For example, the 
PC36 style controllers (because some command intelligence and information
is on the PC card) need to have their on-board firmware match the size
of the tape, be it 60, 125, or 150 MB.  

One nice thing about QIC-02 is that since all of the implementation of 
the QIC-36 command interface is buried inside the drive, any correclty
implemented QIC-02 controller will work with a QIC-02 interface tape
mechanism, regardless of the tape unit's size, without need for firm
ware changes on the controller.

- dimitri rotow

PS - My only regret is that Wangtek doesn't make their 60 MB unit as 
a QIC-02.  Nice line of drives, but I wish we could source them all
as QIC-02's and be done with the "long card" controllers.