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Thread: Sperry/Corona PPC-400 troubleshooting

  1. #1
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    Default Sperry/Corona PPC-400 troubleshooting

    I have in hand a Sperry labled Corona PPC-400

    It has a WDC hard drive controller in it, and a DTK(?) 1.2M floppy drive controller as the only cards.

    The machine has 512K of RAM in it, based on physical observation of the MB

    The hard drive doesn't work.

    When it boots up, there's a banner for the 1.2M card.

    It will then say there's 472K of memory available. Not in front of it, but that number may change slightly from boot to boot.

    I have a floppy with DOS 3.3 on it.

    The machine will say it's loading MS-DOS, and then come up with

    Bad or missing COMMAND.COM file and then ask for the path to COMMAND.COM

    It then gives an "A>" prompt.

    To me, A> is a CP/M prompt not the "A:" prompt I would expect from DOS. This floppy will boot my Compaq Portable III with no issue.

    If I plug the existing drive into the motherboard floppy connector, the drive doesn't work at all.

    Removing the HD controller doesn't make a difference in behavior.

    Jumpers on the MB all seem correct for the config of the machine.

    So my questions are:

    Does the A> prompt make sense? Everything I read says this is a DOS machine, not a CP/M machine - or is this a red herring?

    Might I have bad RAM, since it's only reporting 472K and not the whole 512K? Perhaps the add-on disk controller is using some?

    What else should I check for?

  2. #2
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    I suspect that the "A>" thing is a red herring. What does your AUTOEXEC.BAT file look like?

  3. #3
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    "A>" or "C>" is the default appearance of the dos prompt. If you want to change it, makes sure your autoexec.bat file contains the line "prompt=$p$g"

    It should not complain about a "bad or missing command.com" unless you have put the only copy of command.com in a subdirectory or you have a mismatched command.com from a different version of dos. Are you saying it loads command.com after you type in a location?

    Either way, something sounds wonky with that boot floppy, I'd suggest creating a new fresh boot disk just to be sure.

  4. #4
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    Eh, I read the OP's message again and I think I know what he's saying.

    A> is the prompt given when DOS wants you to type in the location of COMMAND.COM. It's not a standard prompt.

  5. #5
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    If I type in a location for COMMAND.COM, it just cycles with the same error message again.

    I will create a new floppy this weekend (need to dig out an appropriate machine) and see if that makes a difference.

  6. #6
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    It recycles when (a) the COMMAND.COM doesn't verify or (b) the read doesn't work or (c) it can't find the file.

  7. #7
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    OK - the machine will boot with a different floppy- I had a real Gateway DOS 5.0 install disk that worked. Proof that once again one should always check the most obvious things.

    After booting, that floppy drive will not successfully format another 1.2M floppy disk. That, along with the non-functional Miniscribe hard drive will be a problem for another day...

    Thanks all for your insights!

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