Wren IV (?cabling) Problem

[Michael McClary]

In article <8901201904.AA00222 at sapir.> anderson at sapir.psy.jhu.edu writes:
>I'm trying without success to attach a CDC Wren IV drive to a 4/110....
>What happens is that when the drive is cabled to the SCSI connector on the
>machine, it won't even spin up, though it does spin up when not attached
>to the 4/110. Letting it spin up and then attaching it to the machine, the
>Sun reports that it can't find any sd device.

If a Wren doesn't spin up, the first thing to check is whether you've got
the terminator plugged in upside down.  That'll do it on our Jasmine
boxes.  (I think it results from asserting RST.)  Also:  Be sure you've
got power to your terminator.

We're using Wren IVs (packaged both by Jasmine and Relax) on several suns,
including my IV/110.  We use a cable from Monster Cable to go to the
Centronix-style blue-ribbon connector on the Jasmine.  On the Relax, we
start with the Monster Cable, then a home-brew Centronix sex-changer, then
an Apple-style Centronix-to-DB25.

Pinouts of the SCSI-standard 50-pin header (typically found on the drive
proper), SCSI-standard 50-pin "Centronix Style" connector, and the DB-50
(?) used by Sun.  (I didn't check whether Sun does something strange with
anything but varies/TERMPWR.):

	Header	Cntrnx	DB-50	What's connected
	------	------	-----	----------------
	01 02	01 26	01 34	 GROUND	/ -DB(0)
	03 04	02 27	18 02	 GROUND	/ -DB(1)
	05 06	03 28	35 19	 GROUND	/ -DB(2)
	07 08	04 29	03 36	 GROUND	/ -DB(3)
	09 10	05 30	20 04	 GROUND	/ -DB(4)
	11 12	06 31	37 21	 GROUND	/ -DB(5)
	13 14	07 32	05 38	 GROUND	/ -DB(6)
	15 16	08 33	22 06	 GROUND	/ -DB(7)
	17 18	09 34	39 23	 GROUND	/ -DB(P)
	19 20	10 35	07 40	 GROUND	/ GROUND
	21 22	11 36	24 08	 GROUND	/ GROUND
	23 24	12 37	41 25	 GROUND	/ GROUND

	25 26	13 38	09 42   >varies	/ TERMPWR

	27 28	14 39	26 10	 GROUND	/ GROUND
	29 30	15 40	43 27	 GROUND	/ GROUND
	31 32	16 41	11 44	 GROUND	/ -ATN
	33 34	17 42	28 12	 GROUND	/ GROUND
	35 36	18 43	45 29	 GROUND	/ -BSY
	37 38	19 44	13 46	 GROUND	/ -ACK
	39 40	20 45	30 14	 GROUND	/ -RST
	41 42	21 46	47 31	 GROUND	/ -MSG
	43 44	22 47	15 48	 GROUND	/ -SEL
	45 46	23 48	32 16	 GROUND	/ -C/D
	47 48	24 49	49 33	 GROUND	/ -REQ
	49 50	25 50	17 50	 GROUND	/ -I/O

Note that (neglecting right-left) the DB-50 is numbered:

   1   2   3...
    18  19  20...
  34  35  36...

the centronix-style is numbered:

   1   2   3   4...
  26  27  28  29...

and the drive header is numbered:

   1   3   5   7...
   2   4   6   8...

My Sun-4/110 doesn't provide TERMPWR, and leaves DB-50 pin 42 (= header
pin 26, = "Centronix" pin 38) open.  If your drive or terminator is
looking for TERMPWR there, it's out of luck.  (Did older Suns ground that?
If so, Yike!)

According to my copy of the SCSI spec, the "varies" pin has TERMPWR on the
Header.  (Alan Brunner (sp?) from Jasmine was here a couple days ago, and
I think he said that the Wren leaves that pin open.  I haven't tested it
myself.)  It is grounded on my Sun IV/110's connector, and the Monster
cable propagates it through to the Centronix connector.  The SCSI standard
mandates that the pin be an open circuit on a Centronix-style connector,
but warns that some equipment produced before the standard was promulgated
may ground that pin.  Thus, the combination of a Sun IV/110 and a monster
cable violates the SCSI spec, but in a way the spec warns you to expect.

So hook it up this way, check for inverted connectors, no TERMPWR on the
TERMPWR pin at the terminator, TERMPWR on the "varies" pin, and if it
still doesn't work, can I have the drive?  	B-)