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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: Gav on February 23, 2007, 06:51:35 PM
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Ok for a long time i have had various scsi pieces laying around and for xmas i got a scsi hard drive with a 80 pin connection on the back......
I bought an adaptor that plugs in to the back of the hard drive and has a 50 pin? connection for the ribbon cable....
I bought a 25 pin to 50 pin adaptor from amiga kit,so what way does the ribbon cable plug in to the hard drive adaptor?Should the red line be at the right or left side?Same goes for the other end of the cable to the adaptor..
Does this ribbon cable need some sort of teminator?Its so confusing using scsi finding all the bits to the puzzle.
Thanks for any help.
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Oh and btw i have the blizzard scsi 2 kit.
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You need terminate the hd, due the fact they are the last unit in the chain.
If the hd not comes with the resistors pack, then you need an active terminator between the adaptor and the hd itself. Look carefully the drive manual (if you have it not, google the information).
Red wire is the 1st pin, always.
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80 pin is SCA - they're supposed to plug into backplanes and have no termination at all.
On SCSI you always have to terminate both ends - and there must always be exactly two ends.
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The red wire on the ribbon cable should be facing towards the power connector on the HDD. You will also need to terminate the end of the chain, which for you is the HDD. The SCSI HDD will have some sort of jumper selection. Study the Jumpers carefully and set the drive to your chosen SCSI ID and also look carefully for a jumper for termination. Look up the Model Number of the drive in google, you'll probably find a document with the jumper settings outlined clearly.
If you cannot find a terminator on the drive, then you will have to place the drive on any 50pin connector but the last, you will need to apply a passive terminator for a 50 pin ribbon cable to the last plug at the end of the ribbon cable
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I've got the SCSI-IV too and it's an arse to upgrade/maintain.
Luckily it is a SCSI-2 adaptor so will ACTIVE terminate itself so you only have to worry about terminating the hard disk as has been mentioned.
To 'terminate' a SCSI device is just to stop the radio noise from reflecting up and down the wire due to the speed of the electrical signal.
Usually the black header on a 50-pin IDC ribbon has a raised bit on the top bit which is supposed to be facing upwards. A 50-pin IDC female on an adaptor should then have a notch to align with your male.
Try to keep the number of adaptors, heads etc. down as this increases RF reflection. Always make sure that the heads of a ribbon are 10cm apart from each other (a cable should be made this way) and keep the chain below 3 metres long.
I'd stay in Asyncronous mode and don't try Synchronous untill you have a firm grasp of SCSI and the necessities for a high speed connection.
At this point I'm in the same boat as you so this thread should be interesting.
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melange wrote:
The red wire on the ribbon cable should be facing towards the power connector on the HDD.
Thats true of course, but the OP is looking at a 50-pin IDC connector and a molex connector on a SCA adapter, not a HD.
I have seen SCA adapters which do _not_ obey the "pin 1 next to molex" convention :-/ Hopefully, pin 1 is somehow marked on the adapter, or in a "manual".