Image Map Image Map
Page 1 of 2 12 LastLast
Results 1 to 10 of 17

Thread: Tandy 2000 Secondary HD Setup

  1. #1

    Default Tandy 2000 Secondary HD Setup

    All:

    I'm restoring two T2k HD machines and I have a questions about external hard drives.

    Both machines have the HD controller with the connectors on the back. So, I grabbed a 20mb MFM hard drive and a set of cables. The control cable I have has a twist in it between the "C" (outside) and "D" (inside) connectors. I'm guessing that I use "D" and strap the drive for ID=2 (options are 1, 2, 3, 4).

    So, I hooked it up that way and I couldn't format the drive. So, I tested it with other combinations of C/D connector and ID#.

    Has anyone attempted this and if so, what's the right way to do it?

    Thanks.

  2. #2
    Join Date
    Apr 2003
    Location
    Saginaw, MI, USA 48601
    Posts
    8,763
    Blog Entries
    9

    Default

    Yes, I've done it, but it's been a looooooong time...
    IIRC, the T2K uses a straight-thru cable with the drives strapped as DS0 & DS1 (or DS1 & 2, as the case may be). The twisted cable is an IBM thing, which I'm not sure will work on the 2K. If it does, then both drives must be strapped to the second device select, and the drive at the end of the chain must be terminated.

    --T
    Teach your children how to think, not what, and hold 'em close, not tight.
    _____________________________________________

    Please visit the Vintage-Computer Wiki. Contributers welcome.

  3. #3

    Default

    Quote Originally Posted by Terry Yager View Post
    Yes, I've done it, but it's been a looooooong time...
    IIRC, the T2K uses a straight-thru cable with the drives strapped as DS0 & DS1 (or DS1 & 2, as the case may be). The twisted cable is an IBM thing, which I'm not sure will work on the 2K. If it does, then both drives must be strapped to the second device select, and the drive at the end of the chain must be terminated.

    --T
    I knew that the cable twist was an IBM thing which is why I used the "D" connector which is straight-pinned, but I will double-check to make sure the stripe reaches the drive in the right place. The external HD is terminated and strapped for ID=2.

    There is one jumper on the HD controller which is not labeled with anything useful. I don't have a manual for the board. Would you have one I could get a PDF of? In fact, if you have any of the add-in board manuals I'd be happy to scan them and create a little page on my Web site for them. It seems that there's next to nothing out there on the Web on the 2000.

  4. #4

    Default Tandy 2000 Secondary HD Setup

    Quote Originally Posted by Terry Yager View Post
    Yes, I've done it, but it's been a looooooong time...
    IIRC, the T2K uses a straight-thru cable with the drives strapped as DS0 & DS1 (or DS1 & 2, as the case may be). The twisted cable is an IBM thing, which I'm not sure will work on the 2K. If it does, then both drives must be strapped to the second device select, and the drive at the end of the chain must be terminated.

    --T
    After re-reading this a few times I just realized something. How is a chain of internal and external MFM hard drives constructed? Electrically, are they like floppy drives where they sit in a chain? This would mean that I have to remove the internal hard drive to remove the terminator and leave the external drive terminated.

    I think a manual for the HD controller would be a big help.

  5. #5

    Default

    Just a thought, but CAN the 2000 handle 2 drives? Is it possible that it can handle either an internal OR an external, but not both?

    Tandy did do some weird stuff, and the power supply is very under sized.

  6. #6
    Join Date
    Apr 2003
    Location
    Saginaw, MI, USA 48601
    Posts
    8,763
    Blog Entries
    9

    Default

    The external drive has it's own power supply, and it jacks-in to the 2K via a single 50-pin connector, IIRC. Unfortunately, I don't recall ever having to bother with cabling, just plug & play, and it's s'pozed to work.

    Have you tried disconnecting the internal drive to see if it will see the external one all alone?

    --T
    Teach your children how to think, not what, and hold 'em close, not tight.
    _____________________________________________

    Please visit the Vintage-Computer Wiki. Contributers welcome.

  7. #7

    Default

    Quote Originally Posted by Terry Yager View Post
    The external drive has it's own power supply, and it jacks-in to the 2K via a single 50-pin connector, IIRC. Unfortunately, I don't recall ever having to bother with cabling, just plug & play, and it's s'pozed to work.

    Have you tried disconnecting the internal drive to see if it will see the external one all alone?

    --T
    More experimentation. I pulled the power plug on the internal hard drive on the one machine and connected the external hard drive to the secondary port using straight-through cables. The external HD (a 20mb IBM drive) was jumpered for ID=1 (the lowest number possible). And, yes, I made sure the cables were oriented the right way (both sides have keyways or alignment pins).

    I rebooted with a DOS floppy and used hdformat to prepare the external drive. After a moment, it complains that it can't write to the system sectors and the format failed. I can see the head positioner servo on the external drive and it didn't move at all. The external drive is a newly-refurbished and recertified drive so I'm confident it works.

    I have a second T2K that's slightly older but in much better physical condition and I tried the same procedure on with similar poor success.

    This means two things. First, having the internal signal cables connected makes a difference (don't think so, at least not in my experience) or there's some magic in using Tandon hard drives.

    I know that Tandy did some crazy things but could they have somehow locked the controller to the specific model of hard drive?

  8. #8
    Join Date
    Apr 2003
    Location
    Saginaw, MI, USA 48601
    Posts
    8,763
    Blog Entries
    9

    Default

    I know that Tandy did some crazy things but could they have somehow locked the controller to the specific model of hard drive?
    Yes, they could have, and they might have, but I can't swear one way or t'other. I know that the original controller in my ol' Tandy 1000HD would only recognize a drive with 306/4/17. As you well know, they were famous for such shenanigans.

    --T
    Teach your children how to think, not what, and hold 'em close, not tight.
    _____________________________________________

    Please visit the Vintage-Computer Wiki. Contributers welcome.

  9. #9

    Default

    Quote Originally Posted by Terry Yager View Post
    The external drive has it's own power supply, and it jacks-in to the 2K via a single 50-pin connector, IIRC. Unfortunately, I don't recall ever having to bother with cabling, just plug & play, and it's s'pozed to work.

    Have you tried disconnecting the internal drive to see if it will see the external one all alone?

    --T
    Ok, in one last test before my hobby night ended, I pulled the TM502 from one machine and connected it to the external port of the second. I strapped the external drive as ID=2 and tested it with both the terminator and without. In both cases it wasn't recognized as a valid drive, giving a "bad unit error".

    After this process, I have to say that I find the T2k flaky to work with. I don't know whether it's design or that the machines don't ship well. With both machines about 10% of the time I can't get the right amount of memory to register if it's more than 256k and the hard drive subsystem works only about 50% of the time. I wonder if there's a fault in the design of how the card cage connects to the planar.

    Most of the drive errors are "Bad unit error on drive XX" which, reaching back in my memory, means that the controller is active but the drive isn't resetting properly.

    I'm going to read the service bulletins tomorrow to see if anything jumps out at me. Also, I noticed in one of the Computer Catalogs that the external HD system for the T2K is the hulking external HD that's used with the Model III/IV. I wonder if there's something special in there that the HD controller expects rather than directly connecting the controller to the drive itself.
    Last edited by RichCini; December 3rd, 2006 at 06:16 PM.

  10. #10

    Default

    Quote Originally Posted by RichCini View Post
    Ok, in one last test before my hobby night ended, I pulled the TM502 from one machine and connected it to the external port of the second. I strapped the external drive as ID=2 and tested it with both the terminator and without. In both cases it wasn't recognized as a valid drive, giving a "bad unit error".

    After this process, I have to say that I find the T2k flaky to work with. I don't know whether it's design or that the machines don't ship well. With both machines about 10% of the time I can't get the right amount of memory to register if it's more than 256k and the hard drive subsystem works only about 50% of the time. I wonder if there's a fault in the design of how the card cage connects to the planar.

    Most of the drive errors are "Bad unit error on drive XX" which, reaching back in my memory, means that the controller is active but the drive isn't resetting properly.

    I'm going to read the service bulletins tomorrow to see if anything jumps out at me. Also, I noticed in one of the Computer Catalogs that the external HD system for the T2K is the hulking external HD that's used with the Model III/IV. I wonder if there's something special in there that the HD controller expects rather than directly connecting the controller to the drive itself.
    I pulled a copy of the schematics for the 5mb Model 4 hard drive (master unit; I don't have a copy of the 10/20/35mb manuals) and compared the drive interface to that of a standard MFM drive. On the control cable, there's one signal that's not standard (pin 2, RWC; HDSEL8 in the standard) and on the data cable, pin 7 (12v trigger to power-on slave units) and pins 9/10 (TCLK; "reserved" in standard). There are also a few signals swapped in the 50-pin cable versus the 34-pin control cable.

    Given this, maybe the 5mb master unit is unique to the III/IV and when buying an external drive for the T2k, you buy a "slave" unit that has a special cable to activate the electronics (pin 7 connected to +12v).

    Do you have a catalog number of an external drive for the T2K?

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •