From: pcg@decb.aber.ac.uk (Piercarlo Antonio Grandi)
Subject: Re: QIC-36 supported?
Reply-To: pcg@aber.ac.uk (Piercarlo Grandi)
Date: Sat, 4 Sep 1993 19:37:00 GMT

Various people write:

  : >: I have my eye on a tape drive (Wangtek 5150EN, I think) which has a
  : >: QIC-36 interface. Does the Linux kernel support QIC-36? If so, will the
  : >: tape drive work out of the box or does some work need to be done for
  : >: Linux to support QIC-36?

  : >NO, LINUX WILL *NEVER* SUPPORT QIC36 !!!!!!

  : >So, buy the Wangtek (good drive if you get it cheap !) and get either
  : >an external SCSI to QIC36 controller and use the setup with your
  : >SCSI controller or get a (hopefully supported) QIC02 controller that
  : >works with your drive. 

  :   This is inaccurate. On my system, (Gateway 486/33, ISA), the QIC-02
  : driver works fine with a QIC-36 card and Wangtek 5150EN. No SCSI needed. 
  : I don't understand the QIC interfaces well enough to explain why this is
  : an expected result :^), but I was told by "people who know" that the
  : combination should work. And it did.

On Fri, 3 Sep 1993 01:24:14 GMT, Remco Treffkorn
(root@hip-hop.suvl.ca.us) wrote:

  Oh boy, here we go again.. I hope I will get it right in a few words .

Well, you didn't quite... :-)

  The driver talks to the SCSI controller. The SCSI controller talks to
  a card that speaks SCSI on one end and QIC36 on the other. Result:
  Your drive drives...

  The next possibility: The driver talks to a controller that looks like
  a QIC02 interface. QIC02 is a bit more intelligent then QIC36. It
  defines things like certain commands and a protocoll. This controller
  has a QIC36 connector that you connect your drive to. Voila, your dive
  drives!

No. Let's be clear about this: QIC-02 and QIC-36 are standards for the
IO (ISA/EISA/MCA are *system* buses; SCSI is an IO bus; IDE arguably is
an IO bus specification that is almost identical to the ISA system bus
specification) *bus* between the host controller in your PC and the
device controller bolted on the tape drive. With QIC-36 the host
controller is more sophisticated than the drive controller; with QIC-02
the latter is more sophisticated.

Neither QIC-02 nor QIC-36 have *any* relationship whatsoever to the
programmatic interface between the driver in Linux and the host
controller, to the hw interface between the motherboard and the host
controller, or (just to be complete) the format in which data are
recorded on the tape.

Now, what really matters to the Linux driver is the programmatic
interface (which IO ports the host controller uses, which commands, and
so on).

There are several different programmatic interfaces, but *most* host
controllers that communicate with tape drives over a QIC-02 or QIC-36
bus have either the Wangtek/Everex interface or the Archive interface,
which are BTW rather similar to each other. The Linux QIC-02 (a
misnomer) driver supports _both_, irrespective of whether the host
controller actually drives a QIC-02 or QIC-36 bus. In particular most
Wangtek/Everex host controllers have the same interface, whether they
support QIC-02 or QIC-36.

  As you can see, your "QIC36" card is really something that is QIC02 on
  one end and QIC36 on the other.

I think I never heard of a board that enables a QIC-36 tape drive to hang
off a QIC-02 bus, or viceversa; there are at least two that allow a QIC-02
or QIC-36 tape drive to hang off a SCSI bus, but they are rather ancient.

To end: the names of some Everex/Archive host controllers that have (nearly)
the same programmatic interface: 811/831, 409/499.

------------------------------