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Ask the SCSI Expert.


Visit the SCSI SCSI - Small Computer System Interface
SCSI - Shodor Computational Science Institute
SCSI - Small Computer Serial Interface
SCSI - Small Computer Standard Interface
SCSI - Société Canadienne de Santé Internationale (Canadian Society for International Health)
SCSI - Society for Computer Simulation, International
SCSI - Southern California Systems, Incorporated
SCSI - System Can't See It
 Trade Association's web site (www.scsita.org) to ask the SCSI Expert a question.

Q: I'm a software developer. I have an application which queries SCSI devices to gather configuration/asset information.

How do I query a SCS1 device to determine the device's bus speed? I can't find any mention of this in any of the SCSI-3 (hardware) SCSI-3 - An ongoing standardisation effort to extend the capabilities of SCSI-2. SCSI-3's goals are more devices on a bus (up to 32); faster data transfer; greater distances between devices (longer cables); more device classes and command sets; structured documentation; and a structured protocol model.

In SCSI-2, data transmission is parallel (8, 16 or 32 bit wide).
 standards documents. Actually, I don't see any reference to "Ultra" or "Ultra2" or "Ultra160" in any of the SCSI3 standards on www.t10.org.

A: Ultra SCSI, Ultra2 SCSI, and Ultra160 SCSI are the marketing names for the standards.

Following is the data that you need:

Ultra320 SCSI = SPI-4 Fast160 Paced data transfer = 6.25 ns

Ultra160 SCSI/Ultra3 SCS1 = SPI-3 Fast-80DT = 12.5 ns

Ultra2 SCSI = SPI-2 Fast-40 = 25 ns

Ultra SCSI = Fast-20 (Use SPI-2) = 50 ns

Wide Fast SCSI A SCSI interface that transfers at 10 Mbytes/sec rather than 5 Mbytes/sec. The maximum cable length is 9.8 feet. See SCSI. = Fast (Use SPI-2) = 100 ns Calculate transfer period)

Fast SCSI = SPI t Use SPI-2) = 100 ns (Calculate transfer period)

SCSI = SCSI-2 SCSI-2 - Small Computer System Interface 2 /Asynchronous- Narrow)

See the SPI-4 (Revision 7) table 5 for the Transfer period.

Q: We have a cable with the following printed on it: "E119932 AWM AWM - Awaiting Maintenance
AWM - Abrasive Waterjet Machining
AWM - Adult Webmaster
AWM - Advanced Wave Memory
AWM - Advanced Wave Modulation
AWM - Angry White Male
AWM - Apostolic Word Ministries (Warren, MI)
AWM - Appliance Wiring Material
AWM - Arctic Warfare Magnum (Counterstrike weapon)
AWM - Arctic Warfare/Military (sniper weapon)
AWM - Ardent Window Manager
AWM - Association for Women in Mathematics
AWM - Australian War Memorial
 2919 80C 30V VW-1 LOW VOLTAGE COMPUTER CABLE COPARTNER copartner n. one who is a member of a partnership. The prefix "co" is a redundancy, since a partner is a member of partnership. The same is true of the term "copartnership." (See: partner, partnership)."

Does this mean that it only works for LVD LVD - Low Voltage Differential (SCSI)
LVD - Large Visual Display (for hearing- and sight-impaired)
LVD - Laser Video Disk
LVD - Left Ventricular Dysfunction
LVD - Lime Village, Alaska (Airport Code)
LVD - LLS (Laser Leveling System) Vertical Deviation
LVD - Logical Volume Descriptor (OSTA universal disk format)
LVD - Low Velocity Detection
LVD - Low Voltage Detector
LVD - Low Voltage Directive
LVD - Low-Velocity Drop
 devices? We have a SpectraLogic Gator/64000 (HVD HVD - Handspring Visor Deluxe
HVD - Helmet Visor Display
HVD - High Value Detainees
HVD - High Voltage Differential (SCSI)
HVD - Holographic Versatile Disc (Optware)
HVD - Holographic Virtual Disc
HVD - Hub Vortex Dissipater
) tape library that we want to connect to an IBM RS/6000 with a PCI Differential Ultra SCSI (Type 4-L) adapter (IBM Feature Code 6207). Would this cable cause as any problems connecting this system ?

A: The labeling on the cable is for UL certification purposes. Low voltage computer cable means that you cannot use the cable for applications over 30 volts at 80 degrees C, and it has nothing to do with SCSI. If this is a SCSI cable, then it should work fine for connecting HVD SCSI devices.

Q: How does a feed-through terminator work?

A: A feed-through terminator is used on the last bus connection. This type of terminator has both a male and a female connector A plug or socket that contains receptacles. The male counterpart contains pins.

, and is inserted between the last device and the cable.

It is normally used with scanners and low-end devices that do not need to have termination in the device.

I've seen demo cards for termination--for Multimode LVD/SE but no products. Normally on multimode, the termination is built into the cable assembly. This is typically done on the internal, "twist and fiat" cables. The last fiat will have both a 68-pin connector and a terminator that damps onto the cable with IDC (insulation Displacement connector) like the other connectors on the twist and flat cable.) in the "About SCSI" page. Select "Terms and Terminology" which has the speed, the interface and the corresponding cable lengths.

For the relatively newer LVD SCSI standards such as Ultra2. Ultra3, Ultra160 and Ultra320 SCSI it is easy---point-to-point 25 meters, multidrop 12 meters.

www.scita.org
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No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2002, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

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Article Details
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Title Annotation:Tape/Disk/Optical Storage
Publication:Computer Technology Review
Date:Feb 1, 2002
Words:475
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