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Thread: Commodore Pet 4016 won't read memory

  1. #21

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    That's not even a late model, I don't think, because it's punched to limit RAM, which I thought was only early models.
    Be polite and I may let you live.

  2. #22

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    I'd guess you'd need to make an adapter to an EPROM though.
    I don't have a PET schematic handy but the mask ROMs often
    had decoders in some of the select pins.
    I'd need to look at the schematic some. If there was one pin that
    always went low for the entire ROM bank, that would work for the
    select as we expect to stay in the high memory near the boot except
    for the RAMs being tested.
    We don't have to worry about getting into contention with the other
    ROMs that way because we don't intend to be in that address space.
    I guess I have to look at some schematics. You gues have some pointers?
    Dwight

  3. #23
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  4. #24
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    Either remove the CPU and make a small adapter board to decode ROM fxxx and operate the /NOROM pin to disable the onboard ROM(s) or plug a ROM and memory decoder onto the memory expansion connectors (J4 and J9) to achieve the same result.

    No modifications to the PET necessary.

    Dave

  5. #25

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    Could this not be done with PETVet or the other similar board?
    Be polite and I may let you live.

  6. #26

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    Here is an adapter table to plug a standard 2732 or 2732A into
    the chip location UD6. At least for the drawing that MikeS posted.
    All of the pins are 1 to 1 except 18 and 21.

    [code]
    ROM 2732A
    A11 18 21
    CS2 21 nc
    18 ground
    [\code]

    The adapter would be to remove 21 from the bottom socket,
    remove pin 18 from the center socket, a wire from pin 21 of the
    top socket to the bottom socket 18 and run a wire from top
    socket 18 to any socket 12. For safety, I'd pop pin 21 of the
    center socket as well.
    This would be using machine pin type sockets. To pop out unwanted
    pins, I place the socket upside down on a wood board with a hole
    drilled in it. I then pop the pin out by pushing with some needle
    nose pliers.
    Of course you could use the NoRom\ and an external board
    if you didn't want to modify the board.
    Dwight

  7. #27
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    Quote Originally Posted by Dwight Elvey View Post
    Here is an adapter table to plug a standard 2732 or 2732A into
    the chip location UD6.
    One can still find Texas Instruments/National 2532 EPROMs which are pin compatible with Commodore 4K ROMs.

    Also Tynemouth in Great Britain sells a diagnostic board using a microcontroller that fits into the 6502 socket and tests all RAM and ROM memory chips. It also exercises screen RAM. But its cost is about 40 GB pounds so running your code would be much cheaper.

    http://blog.tynemouthsoftware.co.uk/...%20diagnostics

  8. #28

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    Quote Originally Posted by dave_m View Post
    Also Tynemouth in Great Britain sells a diagnostic board using a microcontroller that fits into the 6502 socket and tests all RAM and ROM memory chips. It also exercises screen RAM. But its cost is about 40 GB pounds so running your code would be much cheaper.

    http://blog.tynemouthsoftware.co.uk/...%20diagnostics
    He has some pretty cool stuff. SWMBO has been wanting a new keyboard, for work, because she doesn't like the modern ones. I was going to either give her one of my Model Ms or Model Fs, or buy her a new production one, but now I'm half tempted to give her a Commodore 64, with one of his USB interfaces.

    I grew up across the river from him. The name doesn't ring a bell, but I wonder whether we ever met?

  9. #29

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    That is not a bad price for such a tool. A lot of work goes into such
    a device. Still, if all you want is to run a test of the RAM, I'd go for the
    EPROM on a stack of sockets.
    The TI part is a simpler option if your programmer support it.
    Dwight

  10. #30
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    Quote Originally Posted by Dwight Elvey View Post
    That is not a bad price for such a tool. A lot of work goes into such
    a device. Still, if all you want is to run a test of the RAM, I'd go for the
    EPROM on a stack of sockets.
    The TI part is a simpler option if your programmer support it.
    Dwight
    I have to agree; 2332<>27xx adapters are even available if you don't have any soldering skills/equipment and someone here would probably be happy to supply a programmed 2716/32 RAM tester if the piggyback method doesn't reveal a fault.

    http://store.go4retro.com/23xx-adapter/

    If money's not an issue then by all means the PETVET (if you can find one) or Tynemouth's diagnostic and/or RAM/ROM replacement boards are excellent solutions.

    m

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