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Thread: Weird floppy drive issue on XT computer

  1. #1

    Default Weird floppy drive issue on XT computer

    Hi,

    I've got this XT computer with 2 5.25 360kb floppy drives that has always worked fine. It was in storage for a while and when I opened it I noticed the floppy drive controller card was missing.
    I've got a box full so I tried hooking up the drives again.

    Everything was left untouched, was properly terminated, cabled and jumpered. (both on the floppy drives and on the mainboard dip switch block).

    Both drives are doing their seek on boot, but after that nothing ... when it asks to insert a disk upon boot and I hit enter, I see the LED on the A drive lit up for a while, but the read/write heads are not moving. The disk is spinning.

    I know for a fact that the floppy drive controller + floppy drives work (tried them in another XT). Also, when using the floppy controller from a working XT, it also fails on this particular XT.

    Can something on the mainboard cause this issue ? As I am not seeing anything wrong with the floppy drives, the cables, the controller, and the jumper settings.

    Thx
    Retro enthousiast. Love everything < 486. Learning and sharing on my little channel

  2. #2

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    Quote Originally Posted by RetroSpector78 View Post
    Both drives are doing their seek on boot, but after that nothing ... when it asks to insert a disk upon boot and I hit enter, I see the LED on the A drive lit up for a while, but the read/write heads are not moving. The disk is spinning.
    No error message at that point?
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  3. #3
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    If it has extra cards in it, try reducing it to a minimal configuration. Mis-configured or damaged hard disk systems can sometimes cause floppy booting to freeze.

    If it eventually looks like the problem is really the motherboard, you could test it with the supersoft diagnostic ROMs.

  4. #4

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    No error messages ... have lots of 5.25 inch drives + FDD controllers that work fine... but none of them work with this XT. (and I have used the XT before ... it was always used with 2 5.25inch drives and I never with a hard drive).
    There are no errors ... the drive is seeking, although I have the impression that it kinda "stutters' when the heads are moving back inwards at the end of the seek.
    But the read write heads never move when it wants to read a drive. Only the drive LED lights up for a couple of seconds.

    PSU is outputting a clean 5V and 12V
    Retro enthousiast. Love everything < 486. Learning and sharing on my little channel

  5. #5
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    Are you certain that the floppy is bootable on your system? A corrupted boot sector reads, but then hangs.

  6. #6
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    Quote Originally Posted by RetroSpector78 View Post
    Can something on the mainboard cause this issue ?
    There are some clone XT motherboards where 'turbo' mode needs to be off for reliable floppy operation.

  7. #7
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    A couple more thoughts - *Exactly* what are you trying to boot? Some early OEM DOS versions may hang when run on some machines other than that OEM's, even if the version is "IBM" compatible (often due to BIOS bugs). It is also easy to forget that Windows 9x's DOS 7.x will freeze on a 286 or 8088 machine (but I'm guessing that is not the case since we are talking about 360k disks).

    Also, are these genuine IBM XT computers, or XT clones?

    The specific disk you are trying to use, have you tried booting it on another machine with a 360k drive?

  8. #8

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    Quote Originally Posted by SomeGuy View Post
    A couple more thoughts - *Exactly* what are you trying to boot? Some early OEM DOS versions may hang when run on some machines other than that OEM's, even if the version is "IBM" compatible (often due to BIOS bugs). It is also easy to forget that Windows 9x's DOS 7.x will freeze on a 286 or 8088 machine (but I'm guessing that is not the case since we are talking about 360k disks).

    Also, are these genuine IBM XT computers, or XT clones?

    The specific disk you are trying to use, have you tried booting it on another machine with a 360k drive?
    I was testing with 2 XT clones, and 1 IBM 5155.
    I did try an IBM floppy drive + IBM floppy controller on the XT clone and that also didn't work (while that combo does work on my IBM 5155).

    I did manage to get it booting using a 1 specific floppy controller - floppy drive - floppy disk.

    It seems that some of my ms-dos boot floppies (have half a dozen 3.20 / 3.30 / 6.22 boot floppies on 360kb disks that I regularly use) work on some computers but not on others.
    Perhaps this one was even more picky.
    It also turned out that 3 floppy controllers were bad (there were no errors on startup, but they weren't able to initialise the disks (no seek / no attempt to read).

    Problem with this type of trouble shooting is that you need to take into account the floppy drives, the jumpers, the cables, the controllers, the PC and perhaps most importantly the quality of the floppy disks themselves.
    Think at some point I assumed that all of these floppies worked fine, but didn't realise that some did not and a corrupted boot sector could cause the R/W heads to halt and not do anything. (making you think there is an issue with the drive and/or controller/pc).

    Will try to do a more methodical way of testing this afternoon it with all of that in mind to determine what really works and what really doesn't work.
    Retro enthousiast. Love everything < 486. Learning and sharing on my little channel

  9. #9

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    Go to a working, reliable machine and test your boot disk(s) with Norton DT.EXE (Disk Test) or something similar. When you are sure you have an error free boot disk use it to start the troublesome computer. After using it, if it still doesn't work properly on the troublesome computer, test it again with DT.EXE on the good machine to be sure that the computer with the issue didn't somehow foul the boot disk. At least this way you can rule out the disk, itself.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  10. #10

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    Hm, check the power supply voltages? If I remember correctly, older (like original IBM) floppy controllers needed negative voltages as well. If they are missing (maybe not from the PSU, but missing from the ISA slots), it could affect the floppy controllers.

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