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Using IDE cable 'back to front'

Discussion in 'Desktop & Laptop Computers Forum' started by Gary Lightfoot, Sep 5, 2003.

  1. Gary Lightfoot

    Gary Lightfoot
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    In my new htpc case, I have to have the two hard drives side by side, and not one above the other. One is jumpered as master, and the other has no jumper as it is the slave (both Seagate Barracuda drives).

    All the IDE cables I have have the long section between the blue connector and the grey connector, and the short section between the grey and black.

    I thought I'd put the black into the mobo, then connect the primary drive onto the grey one. The slave drive will be connected to the blue connector which now easily reaches it.

    I booted up with just the primary drive connected, and everything was fine.

    I powered down, then connected the slave drive to the blue connector. On boot, neither drive is detected. Disconnect the slave drive, and all is well again.

    I then removed the slave drive and layed it on top of the master drive, and connected the cable with the blue end into the motherboard and the grey connection into the master, and black into the slave. It boots up and runs fine. I even formated the slave drive into NTFS from Windows.

    So, what's stopping me from turning the cable round?

    It looks like I'm going to have to buy another cable - despite having half a dozen of them including some nice round ones. :)

    Gary.
     
  2. Paul D

    Paul D
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    Hi Gary

    If your cable has three different coloured plugs, it's a "cable select" type. Meaning they have to be connected in this order, if you have two drives etc.

    The blue connector is for your host bus adapter (using a connector on your motherboard).
    The black connector at the other end is for your master device, usually the hard drive you boot from.
    The grey connector is for an optional slave device if you have a second hard drive.


    Hope this helps...
     

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  3. nutcase_1uk

    nutcase_1uk
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    From what I remember of the ATA 66/100/133 cables (with the 40 way connectors, 80 conductor cable), the motherboard (blue) end is wired differently to the drive ends, so I'm not suprised it doesn't work.
     
  4. Gary Lightfoot

    Gary Lightfoot
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    In order for cable select to work on the Seagate drives, you have to have them jumpered in the cable select position. I have them as master and slave so the cable select method isn't used.

    If the blue end of the cable is wired differently, then that may explain why just using the black and grey connections works OK, but not when the blue is. I'm not sure how this is done though, as the cable is flat and all connectors appear to be press fitted.

    I'll have to try and find an IDE cable with a longer drive connector by the looks of it. :(

    EDIT: I decided to put it on the secondary IDE with the DVD drive, and it all connected up with no problems - cables reach, and DVDs play with no problems as far as I can see. :)

    Cheers guys.

    Gary.
     
  5. CENSORED

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    Check the jumper on your master HD closely. Some HD's have a setting for master when only one drive is being used, and another setting for master if a slave drive is also being used. In other words two jumper settings for master depending if a second drive is also installed. Sounds odd I know but I recently installed a Western Digital drive on a master/slave setup and nearly pulled my hair out until I did a double take on the drive label.
     
  6. Gary Lightfoot

    Gary Lightfoot
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    I know what you mean - the Fujitsu drive I had had a similar configuration IIRC. Seagate have it marked on the drive, and I did check that everything was correct after I had the problem.

    It seems odd that it won't work back to front considering that the cables have push fit connectors on them and all 'pins' appear to be in parallel. So how does it know which drive is where except by the master and slave jumpers? CS must be quite clever too...

    Cheers.

    Gary.
     
  7. Epithet

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    Try searching on google for "cable select". You'll find numerous articles like this one.

    http://www.firmware.com/support/bios/cablesel.htm

    Apparently its all about the wiring of pin 28 which is different for the slave and master sockets. Since pin 28 is not in the centre of the socket I guess that reversing the cable will lead to incorrect connection of pin 28 at the m/b and also at the master socket ends of the cable.

    Epithet
     
  8. Gary Lightfoot

    Gary Lightfoot
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    Ahhh - that sounds like the culprit then.

    Thanks for the link. :)

    Gary.
     
  9. dnrc

    dnrc
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    The cable is wired straight through on all plugs and should work fine in any orientation. This doesn't mean it will though as it will depend on your board and the drives you are using.

    The colour coding is on the cable for guide purposes.

    Cable select has nothing to do with it as you probably don't have a cable select cable. The way to tell is that one wire (someone said 28 before, i cannot remember) will be cut / not connected.
     
  10. Bursar

    Bursar
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    Here's the official response to that:
    Connector Assignments and Color Coding: For the first time, the 80-conductor cable defines specific roles for each of the connectors on the cable; the older cable did not. Color coding of the connectors is used to make it easier to determine which connector goes with each device:
    Blue: The blue connector attaches to the host (motherboard or controller).
    Gray: The gray connector is in the middle of the cable, and goes to any slave (device 1) drive if present on the channel.
    Black: The black connector is at the opposite end from the host connector and goes to the master drive (device 0), or a single drive if only one is used.

    There are a couple of reasons why this coding was done. It is not a good idea to connect a single drive to the middle connector on a ribbon cable, because the "stub" of left-over, unconnected cable causes signaling problems. With Ultra DMA this "stub" connection is not just "not recommended", it is illegal: a single device must be at the end of the cable. The other reason is that since these cables support cable select inherently, the position of each drive on the cable matters if cable select is being used. With these two needs combined, it just made sense to design the cable so that drive positioning was explicitly clear.
     
  11. Gary Lightfoot

    Gary Lightfoot
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    Thanks for the info.

    I think I have my single drive on the wrong connector - I'll get round to swapping it sometime... :)

    Gary.
     
  12. Paul D

    Paul D
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    I sure this is what i said in my answer!:D
     
  13. Gary Lightfoot

    Gary Lightfoot
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    Yes you did, but I didn't want you thinking you were a smart arse. :D

    Actualy it was my fault - having re-read it, I realise I didn't read it correctly - I saw 'cable select' and thought you were suggesting that I'd not configured the drives correctly, so thought that wasn't it.

    I'll sit up and read your comments more diligently in future. ;)

    Gary.
     

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