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SCSI termination
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Grizzled Veteran
Join Date: Jun 2001
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Mar 22, 2004, 05:05 PM
 
I am going to be trying to get a powermac 8500 to use X with xpostfacto.
I know one of the main things to look out for is proper SCSI termination, but apart from ID I am not sure what the entails.
I am going to be using two internal SCSI hard drives, will I need an internal active terminator?

I have two active Centronics 50 external terminators but none that would fit inside the case.
     
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Join Date: Sep 2003
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Mar 22, 2004, 11:20 PM
 
Originally posted by Langdon:
I am going to be trying to get a powermac 8500 to use X with xpostfacto.
I know one of the main things to look out for is proper SCSI termination, but apart from ID I am not sure what the entails.
I am going to be using two internal SCSI hard drives, will I need an internal active terminator?

I have two active Centronics 50 external terminators but none that would fit inside the case.
I had a 8500 with two scsi internal drives and I never did anything for termination. I think one of the drives did it automatically. Give it a try without anything special first, then if need by go and buy something. Best of luck.

nt
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Mac Elite
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Mar 23, 2004, 12:58 AM
 
On internal drives it's usually just a matter of setting a jumper. Look over the drives and there's usually a little pictogram of how to set the drive to terminate. Remember to terminate only the drive at the end of the chain.
     
Ra
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Mar 25, 2004, 03:26 AM
 
Usually the second drive needs termination, and most SCSI drives use jumpers (very small, black color, square sockets). There should be a diagram or a label on the drive, with information about termination, jumpers, etc.

When you look at the pins at the back of the drive (usually six pins to set the ID):

ID 0 = no jumpers over the 6 pins used (pins up/down)
ID 1 = a jumper over the first set of pins on the left side
ID 2 = a jumper on the center pins (up/down)
ID 3 = jumper at the left, and jumper on the center pins
ID 4 = jumper on the pins at the right
ID 5 = jumper at the left, jumper at the right (center not used)
ID 6 = jumper on the center, and jumper at the right

The first devise (the main drive) should be ID 0, and the second drive should be 1, 4, 5, 6 or so. ID 0 drive is usually terminated already, but sometimes the second drive will need termination, too, since it's the last drive on the internal chain. The CD drive is ID 3, so you may not want to use that ID number. The computer itself should be ID 7 (I think), so don't use that number when jumping pins.

Finally, do a Google search on "SCSI hard drive pin jumpers," or maybe "SCSI hard drive termination," etc.

For external SCSI chains, the first as well as the last devise in the chain should be terminated. Some external SCSI devises have a termination switch at the back (my Zip 100 has one), while some others require the use of a termination plug.

As with all electrical devises, if you make s mistake you could damage the drive, so it's not a bad idea to let a technician help you.
     
Posting Junkie
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Mar 29, 2004, 03:49 AM
 
Originally posted by Ra:
For external SCSI chains, the first as well as the last devise in the chain should be terminated.
Huh? I thought that the internal terminator inside the Mac serves as the terminator on one end of the chain, and you should only put a terminator on the last one.

Ticking sound coming from a .pkg package? Don't let the .bom go off! Inspect it first with Pacifist. Macworld - five mice!
     
Ra
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Apr 2, 2004, 01:58 AM
 
The external SCSI chain on my computer is as follows:

LaCie hard drive-Zip drive-Film scanner-flat bed scanner. The hard drive is terminated, and so the flat-bed scanner. Perhaps I am wrong, but whenever both are not terminated, the computer works erratically.

I was having such a problem before, and a computer tech. friend of mine told me to terminate both, because the computer could not tell which devise was the first one on the SCSI chain. He told me, "the computer needs to find the beginning and the end of the SCSI chain." My computer and the external SCSI chain have worked flawlessly for several years now.

I just searched "SCSI chain termination" in the web, and found the answer (both should be terminated):
http://www.adobe.com/support/techdocs/ba02.htm

For internal termination (one terminated);
http://support.clubmac.com/display.asp?r=517
( Last edited by Ra; Apr 2, 2004 at 02:16 AM. )
     
   
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