SCSI FAQ 27-38

COMP.PERIPHS.SCSI FAQ

Contents:


27) How can I contact UltraStor?

 Answer From: Ultrastor

     UltraStor Corporation
     13766 Alton Parkway suite 144
     Irvine, CA 92718


     General        (714) 581-4100
     Tech. Support  (714) 581-4016
     FAX            (714) 581-4102
     BBS            (714) 581-4125
 
     email:     ultrastor@primenet.com
     finger:    ustor@primenet.com
     ftp:       ftp.primenet.com:users/u/ustor
 
Rob McKinley (mckinley@spss.com) writes that UltraStor is now out of Chapter 11.


---------
Ben Mehling (bmehling@uci.edu) writes:

I think I can comment here...  I do not think these numbers are 
good anymore.  The 4100 line will get you Power I/O (an unrelated 
Adaptec holding) and the 4016 line may get you a dead-end answering 
service.  The company is no longer active (as far as I know).  The 
primenet account is alive, but again not active.  These links are to
the "Unauthorized" UltraStor site.  This site is in no way affiliated
with UltraStor or its holding companies.  It is a free "mirror" site
for distribution of drivers and information.  (hint: we are trying to
help out, not provide tech support.) Try:

UltraStor@kuci.uci.edu (unauthorized).
www.kuci.uci.edu/~ustor/ UltraStor (unauthorized).
falco.kuci.uci.edu/users/ustor UltraStor (unauthorized).

Thanx -Ben
bmehling@uci.edu

28) What is the address and telephone number of WANGTEK?

 ANSWER From: "Terry Kennedy, Operations Mgr" <uunet!spcvxa.spc.edu!TERRY>

Wangtek can be reached at:

  WANGTEK Incorporated
  41 Moreland Road
  Simi Valley, CA 93065
  (805) 583-5255 [voice]
  (805) 583-8249 [FAX]
  (805) 582-3620 [BBS]
  (805) 582-3370 [BBS] DISCONNECTED
 
  WANGTEK-Europe
  Unit 1A, Apollo House
  Calleva Industrial Park
  Aldermaston, Reading
  RG7 4QW England
  (44) 734-811463 [voice]
  (44) 734-816076 [FAX]
  851-848135 [telex]

More Info from: Peter Dyballa (pete@riese.thi.informatik.uni-frankfurt.de) Wangtek is now owned by Rexon. Try looking at ftp.rexon.com. They apparently also have a BBS: (805) 582-3620.

29) What is the address and telephone number of Western Digital?

 ANSWER From: Daniel Miller (MILLER_DA@A1.WDC.COM)

Address:

          Western Digital Corporation
          8105 Irvine Center Drive
          Irvine, CA  USA   92718

Phone Numbers:

          Voice             714-932-5000
          Tech Support      800-ASK-4-WDC
          Tech Support FAX  714-932-4012

Online Services:

          Tech Support BBS  714-753-1234   (up to 28.8 KBS)
          Internet          http://www.wdc.com
          FTP               ftp.wdc.com
          AOL  (keyword)    WDC or Western Digital
          MSN  (go word)    WDC

30) What is the phone number of DPT?

 ANSWER: From: nglhs@alf.uib.no

DPT
voice: (407) 830-5522
FAX:   (407) 260-5366

31) What is the phone number of Future Domain?

 ANSWER: From: garyf@wang.com (Gary Field)

Voice:        (714) 253-0400
BBS:          (714) 253-0432
Tech Support: (714) 253-0440

(For all countries - no foreign tech support offices) Foreign callers should mention that they are calling internationally when they call in.

32) How can I contact Micropolis?

 ANSWER: From: Richard Ravich (Richard_Ravich@microp.com)

Tech Support: (818) 709-3325
E-mail:       Richard_Ravich@microp.com

33) What is FAST SCSI?

 ANSWER From: kev@hpcpbla.bri.hp.com (Kevin Jones)

There are 2 handshaking modes on the SCSI bus, used for transferring data: ASYNCHRONOUS and SYNCHRONOUS. ASYNCHRONOUS is a classic Req/Ack handshake. SYNCHRONOUS is "sort of" Req/Ack, only it allows you to issue multiple Req's before receiving Ack's. What this means in practice is that SYNCHRONOUS transfers are approx 3 times faster than ASYNCHRONOUS.

SCSI1 allowed asynchronous transfers at up to 1.5 Mbytes/Sec and synchronous transfers at up to 5.0 Mbytes/Sec.

SCSI2 had some of the timing margins "shaved" in order that faster handshaking could occur. The result is that asynchronous transfers can run at up to 3.0 Mbytes/Sec and synchronous transfers at up to 10.0 Mbytes/Sec. The term "FAST" is generally applied to a SCSI device which can do syncrhonous transfers at speeds in excess of 5.0 Mbytes/Sec. This term can only be applied to SCSI2 devices since SCSI1 didn't have the timing margins that allow for FAST transfers.

34) SCSI terminators should measure 136 ohms?

 ANSWER From: stevel@coos.dartmouth.edu (Steve Ligett)

Yes, that is what you should measure. Let's see how that is so. The terminator contains 18 220-ohm resistors from signals to termpower, and 18 330-ohm resistors from those signals to ground. I've drawn that below:

termpower--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
           |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
220 ohms-> R  R  R  R  R  R  R  R  R  R  R  R  R  R  R  R  R  R
           |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
signals -> o  o  o  o  o  o  o  o  o  o  o  o  o  o  o  o  o  o
           |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
330 ohms-> R  R  R  R  R  R  R  R  R  R  R  R  R  R  R  R  R  R
           |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ground   --+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

When you measure from any one signal to termpower, you aren't measuring that resistor in isolation, you are measuring that resistor IN PARALLEL with the combination of the corresponding 330 ohm resistor plus 17 220+330 ohm resistor pairs in series. I've redrawn the schematic to make this easier to see:

termpower--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
           |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
           |  R  R  R  R  R  R  R  R  R  R  R  R  R  R  R  R  R <- 220 ohms
           |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
           |  o  o  o  o  o  o  o  o  o  o  o  o  o  o  o  o  o
           |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
           |  R  R  R  R  R  R  R  R  R  R  R  R  R  R  R  R  R <- 330 ohms
  220 ohms R  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
           |  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-- ground
           |  |
           |  R <-- 330 ohms
           |  /
signal ->  o-/
 
<our resistor><--------- other stuff that's in parallel ---------->

We're trying to measure that one resistor from a signal to termpower, but there's a ton of other stuff in parallel. The resistance of that"stuff" is 330 + 550/17 ohms (the 330 ohm resistor, in series with a parallel combination of 17 550 ohm resistors). The general formula for the equivalent of two resistances in parallel is r1*r2/(r1+r2). Whipping out my trusty spreadsheet, I find that the "stuff" has a resistance of about 362 ohms, and that in parallel with 220 ohms is about 137 ohms.

35) What's the difference between 'normal' scsi and differential scsi?

 ANSWER From: ralf@wpi.WPI.EDU (Ralph Valentino)

"Normal" SCSI is also called "Single-ended" SCSI. For each signal that needs to be sent across the bus, there exists a wire to carry it. With differential SCSI, for each signal that needs to be sent across the bus, there exists a pair of wires to carry it. The first in this pair carries the same type of signal the single-ended SCSI carries. The second in this pair, however, carries its logical inversion. The receiver takes the difference of the pair (thus the name differential), which makes it less susceptible to noise and allows for greater cable length.

36) What are the pinouts for differential SCSI?

 ANSWER From: ralf@wpi.WPI.EDU (Ralph Valentino)

                Differential SCSI Connector Pinouts
 
+-------+---------+-------+---------+  +-------+---------+-------+---------+
| SCSI  |         | MINI  |         |  | SCSI  |         | MINI  |         |
| SIGNAL| DD-50P  | MICRO | DD-50SA |  | SIGNAL| DD-50P  | MICRO | DD-50SA |
+-------+---------+-------+---------+  +-------+---------+-------+---------+
| -GND  |    2    |  26   |   34    |  | (open)|    1    |   1   |    1    |
| -DB(0)|    4    |  27   |    2    |  | +DB(0)|    3    |   2   |   18    |
| -DB(1)|    6    |  28   |   19    |  | +DB(1)|    5    |   3   |   35    |
| -DB(2)|    8    |  29   |   36    |  | +DB(2)|    7    |   4   |    3    |
| -DB(3)|   10    |  30   |    4    |  | +DB(3)|    9    |   5   |   20    |
| -DB(4)|   12    |  31   |   21    |  | +DB(4)|   11    |   6   |   37    |
| -DB(5)|   14    |  32   |   38    |  | +DB(5)|   13    |   7   |    5    |
| -DB(6)|   16    |  33   |    6    |  | +DB(6)|   15    |   8   |   22    |
| -DB(7)|   18    |  34   |   23    |  | +DB(7)|   17    |   9   |   39    |
| -DB(P)|   20    |  35   |   40    |  | +DB(P)|   19    |  10   |    7    |
|  GND  |   22    |  36   |    8    |  |DIFSENS|   21    |  11   |   24    |
|  GND  |   24    |  37   |   25    |  |  GND  |   23    |  12   |   41    |
|TERMPWR|   26    |  38   |   42    |  |TERMPWR|   25    |  13   |    9    |
|  GND  |   28    |  39   |   10    |  |  GND  |   27    |  14   |   26    |
| -ATN  |   30    |  40   |   27    |  | +ATN  |   29    |  15   |   43    |
|  GND  |   32    |  41   |   44    |  |  GND  |   31    |  16   |   11    |
| -BSY  |   34    |  42   |   12    |  | +BSY  |   33    |  17   |   28    |
| -ACK  |   36    |  43   |   29    |  | +ACK  |   35    |  18   |   45    |
| -RST  |   38    |  44   |   46    |  | +RST  |   37    |  19   |   13    |
| -MSG  |   40    |  45   |   14    |  | +MSG  |   39    |  20   |   30    |
| -SEL  |   42    |  46   |   31    |  | +SEL  |   41    |  21   |   47    |
| -C/D  |   44    |  47   |   48    |  | +C/D  |   43    |  22   |   15    |
| -REQ  |   46    |  48   |   16    |  | +REQ  |   45    |  23   |   32    |
| -I/O  |   48    |  49   |   33    |  | +I/O  |   47    |  24   |   49    |
|  GND  |   50    |  50   |   50    |  |  GND  |   49    |  25   |   17    |
+--------------------------------------------------------------------------+

Please note that I can only verify the DD-50P connector. The Mini Micro and DD-50SA pinout above is a pin for pin mapping from the SCSI pinout in the FAQ.

How to tell if you have a single ended or differential drive:

Use an ohm meter to check the resistance between pins 21 & 22. On a single ended system, they should both be tied together and tied to GND. On the differential drive, they should be open or have a significant resistance between them. Note that most drives today are single ended so you usually only have to worry about this with old drives scavenged from other systems.

[ Editor's note: The preceeding comment about differential drives being old is not valid. Differential drives are less common than single-ended ones, because they are mainly used only where longer cable runs are necessary, and they are not generally used in PCs, but state of the art drives are available with differential interfaces. Generally only the higher performance drives have a differential option because of the added cost. - Gary Field ]

37) What are the pinouts for 'normal' SCSI connectors?

 ANSWER From: snively@scsi.Eng.Sun.COM (Bob Snively)

Originally dated May 23, 1990

The connector families described by the drawings have standard pin numberings which are described the same way by all vendors that I have encountered. The SCSI-2 specification identifies the standard numbering, using that convention. It happened to be documented by AMP, but all the vendors use the same convention.

The following diagrams have the outline drawings of connector sockets at the bottom. This is really for reference only, because the connector sockets and plugs are both specified as to their numbering and usually are labeled.

There are some minor problems in naming the microconnector conductor pairs, which I have corrected in the enclosed diagram. All the conductor pairs of the Mini-Micro (High Density) connector are in fact passed through on the cables. SCSI-2 defines the RSR (Reserved) lines as maybe ground or maybe open, but they are still passed through the cable. Most present standard SCSI devices will ground those lines.

-----------  microSCSI to SCSI Diagram   -------------

                       SCSI Connector Pinouts
 
+-------+---------+-------+---------+  +-------+---------+-------+---------+
| SCSI  |         | MINI  |         |  | SCSI  |         | MINI  |         |
| SIGNAL| DD-50P  | MICRO | DD-50SA |  | SIGNAL| DD-50P  | MICRO | DD-50SA |
+-------+---------+-------+---------+  +-------+---------+-------+---------+
| -DB(0)|    2    |  26   |   34    |  |  GND  |    1    |   1   |    1    |
| -DB(1)|    4    |  27   |    2    |  |  GND  |    3    |   2   |   18    |
| -DB(2)|    6    |  28   |   19    |  |  GND  |    5    |   3   |   35    |
| -DB(3)|    8    |  29   |   36    |  |  GND  |    7    |   4   |    3    |
| -DB(4)|   10    |  30   |    4    |  |  GND  |    9    |   5   |   20    |
| -DB(5)|   12    |  31   |   21    |  |  GND  |   11    |   6   |   37    |
| -DB(6)|   14    |  32   |   38    |  |  GND  |   13    |   7   |    5    |
| -DB(7)|   16    |  33   |    6    |  |  GND  |   15    |   8   |   22    |
| -DB(P)|   18    |  34   |   23    |  |  GND  |   17    |   9   |   39    |
|  GND  |   20    |  35   |   40    |  |  GND  |   19    |  10   |    7    |
|  GND  |   22    |  36   |    8    |  |  GND  |   21    |  11   |   24    |
|  RSR  |   24    |  37   |   25    |  |  RSR  |   23    |  12   |   41    |
|TERMPWR|   26    |  38   |   42    |  |  OPEN |   25    |  13   |    9    |
|  RSR  |   28    |  39   |   10    |  |  RSR  |   27    |  14   |   26    |
|  GND  |   30    |  40   |   27    |  |  GND  |   29    |  15   |   43    |
| -ATN  |   32    |  41   |   44    |  |  GND  |   31    |  16   |   11    |
|  GND  |   34    |  42   |   12    |  |  GND  |   33    |  17   |   28    |
|  BSY  |   36    |  43   |   29    |  |  GND  |   35    |  18   |   45    |
| -ACK  |   38    |  44   |   46    |  |  GND  |   37    |  19   |   13    |
| -RST  |   40    |  45   |   14    |  |  GND  |   39    |  20   |   30    |
| -MSG  |   42    |  46   |   31    |  |  GND  |   41    |  21   |   47    |
| -SEL  |   44    |  47   |   48    |  |  GND  |   43    |  22   |   15    |
| -C/D  |   46    |  48   |   16    |  |  GND  |   45    |  23   |   32    |
| -REQ  |   48    |  49   |   33    |  |  GND  |   47    |  24   |   49    |
| -I/O  |   50    |  50   |   50    |  |  GND  |   49    |  25   |   17    |
+-------+---------+-------+---------+  +-------+---------+-------+---------+
 
 * NC = NOT CONNECTED
 
 CONNECTOR TYPES:
                                  DD-50SA
                       +------------------------+            MINI-MICRO
       DD-50P          |   -------------------  |     +--------------------+
   +-------------+     |17 \o o o o o o o o o/1 |     |  _________________ |
 49| o o o o o o |1    | 33 \ o o o o o o o /18 |     |25\ o o o o o o o /1|
 50| o o o o o o |2    |  50 \o o o o o o o/ 34 |     | 50\o o o o o o o/26|
   +-------------+     |      -------------     |     |   --------------   |
                       +------------------------+     +--------------------+

Notes:

38) What are pinouts for Macintosh Plus SCSI Connector?

 ANSWER From: Gary Field (garyf@wang.com)

Note that this connector is NOT COMPLIANT WITH ANY SCSI STANDARD! The grounding is insufficient and does not allow for proper twisted-pair transmission line implementation. It is recommended that a short adapter cable be used to convert to the more common Centronics style 50 pin connection rather than extend the 25 pin connection any further than necessary. The Macintosh Plus used a NCR 5380 SCSI chip controlled by the MC68000 processor.

+-------+---------+
| SCSI  |         |
| SIGNAL| DB-25S  |
+-------+---------+                     DB-25S (female)
| -DB(0)|    8    |            _____________________________
| -DB(1)|    21   |          13\ o o o o o o o o o o o o o /1
| -DB(2)|    22   |           25\ o o o o o o o o o o o o /14
| -DB(3)|    10   |              ------------------------
| -DB(4)|    23   |             View from rear of computer.
| -DB(5)|    11   |
| -DB(6)|    12   |
| -DB(7)|    13   |
| -DB(P)|    20   |
|  GND  | 7,9,14  |
|  GND  |16,18,24 |
| -ATN  |    17   |
|  BSY  |    6    |
| -ACK  |    5    |
| -RST  |    4    |
| -MSG  |    2    |
| -SEL  |    19   |
| -C/D  |    15   |
| -REQ  |    1    |
| -I/O  |    3    |
+-----------------+

Pin 25 is NOT CONNECTED in the Mac implementation. Some Future Domain clones connect TERMPWR to pin 25, but are otherwise the same.

Please feel free to mail us with suggestions, comments, and help. Give us a few days to respond,this account is not constantly active. Thanx.