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EASY Adaptec SCSI card question

Posted on 1999-01-03
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Last Modified: 2010-04-27
I have an Adaptec 2940UW SCSI card OEM.

Is 2940U (ultra) and 2940 UW (Ultra Wide) the same thing as I am confused.  Also what are the listings for SCSI,

U
UW
SCSI W
SCSI II
SCSI III

Is the above correct?  I want to buy a SCSI HD, what type should I get to match the performance of my card?
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Question by:ey143
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6 Comments
 
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Expert Comment

by:khemicals
ID: 1014529
you want scsi III UW

there is too much information on SCSI for me to just list a little and feel like I gave you what you need... so instead I will give you the URL of a helpful FAQ with more information on SCSI than even I care to know: http://www.ultranet.com/~gfield/gary/scsifaq.html
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Expert Comment

by:Jason_S
ID: 1014530
2940U is Ultra 50 Pin interface only.  2940UW is Ultra 50 Pin interface, with an Ultra-Wide 68 pin interface connector also.  Both are internal SCSI connectors.  There is a UW external 68 pin connector on the card also.  Only two connectors can be used at any one time.

Any questions, let me know.
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Author Comment

by:ey143
ID: 1014531
SCSI III is definately not what I can use.  I am told that SCSI II is my limit for HDs etc.
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Expert Comment

by:Jason_S
ID: 1014532
To get the most out of the card, get a 68 pin UW drive.  Don't forget to set the card for UW (@ 40MB)in the card BIOS (CTRL-A).
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Accepted Solution

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rjhawkin earned 40 total points
ID: 1014533
For a really well put together page on what all of the SCSI types are and what you can expect for maximum throughput of the various types, take a look at the link below.  Also at the second link, you can get information about how long of a cable chain is possible for the different types. It is not necessary to use a UW controller at the maximum rate of the controller, however if you try and run the controller faster than the max of the slowest device you could get errors.  This is the reason 'real' performance servers use 2 controllers, one for the slower SCSI-II devices, and one (sometimes a UW) for the drives.

An interesting feature of the 2940UW is that it can do data transfers from drive to drive without swapping it out to the processor for switching, aint DMA wonderful?

Reguarding Jason_S's comment, you can use only one of the internal connectors at any time. You cannot hook things to both int. connectors even if you dont use the external.


http://www.seagate.com/support/disc/faq/scsirev.shtml

http://www.seagate.com/support/disc/faq/scsi_interface_cable.shtml
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Expert Comment

by:rjhawkin
ID: 1014534
I have recently learned that I was mistaken on one point with the 2940 series from Adaptec. You can use any 2 connectors available on the card. if you try the third, you will run into problems with reflection of electrical signals off of the "T" style junction
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