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Thread: Terminators??? What kind for what?

  1. #1
    Join Date
    Dec 2002
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    Fairfield, CT, USA
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    I want to ask you about this. I have been a mac user for a while, and have accumulated a bunch of the 50 pin "passive" terminators.

    But I was browsing a source of supplies, and they offer standard 50 pin terminators in "Passive", "Differential", and "Active".

    I know what's in a passive terminator (resistors to match the impedence of the SCSI line)... but what's in the Differential, and active ones... and what's the difference in performance of the drives?

    Reason I ask is that my drives aren't performing as fast as they should. Speed check shows about 5mgs a second, but the drives are capable of 20 mgs a second.
    Also, the speed test says the drives are running in "async"

    Will going to a different terminator change the mode of running to a faster mode, and what kind off terminator wouls be best.

    IT's a 9600, with original mach 5 board, and I'm using the out board SCSI line (SCSI:1)

    There 4 drives in the chain, plus several other devices, and a scanner.
    CatMan



    [This message has been edited by CatMan (edited 18 January 2003).]

  2. #2
    Join Date
    Jan 2001
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    I don't know the9600 Specs but on-board SCSI is apt to be 'constrained' and the only time you get the theoretical maximum performance is on a bare volume usually.

    You would only get 20MB/s if using an UltraSCSI (Blue Note, 2930), anything that runs at 20 MHz. An active terminator or mid-stream active model can 'tame' and help with longer and more complex SCSI situations. Anytime you have 4 drives, scanner, and "other devices" you are well into voodoo land. The longer it is the active terminator helps retain single strength and whatever else. (I hope they aren't all on one bus for goodness sake!)

    Try browsing through the SCSI Voodoo and see if that helps. Info on terminators

  3. #3
    Join Date
    Sep 2002
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    kerrville
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    Catman:

    I have a 9600/300 attached to a scanner and hp9600se cdrw (meant for Wintel's). I use the cdrw's built in auto termination and the scanner's block type inline terminator (not at the same time). They both work. Because my cdrw is 12x8x32 I get stopwatch clocked transfers of 2MB/sec copying data from a cd to my internal fast HD. My internal HD when duplicating a file gets 3.5MB max., but a benchmark test will say 6-7MB/sec read/write. External scsi on these legacy Mac models are 5MB/sec. and internal is 10MB/sec. You might try moving the drives to the internal scsi bus.

    [This message has been edited by tlooknbill (edited 18 January 2003).]

  4. #4
    Join Date
    Dec 2002
    Location
    Fairfield, CT, USA
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    tlooknbill...

    Thanks for your edjamacational reply. I did NOT realize the the external SCSI was limited to 5 mgs. That must be what is limiting the drives (that are rated at 20mgs).

    I have an unused Adaptec card that will run at 20 mgs. I think I will install that card, and put the drives on it, and leave the other stuff (Scanner, CDR, etc) on the external line from the mac bus. Thanks for your reply, I think you have solved my problems (for today ).

    CatMan

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