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  1. Cloning a PAL/HAL (Part 3)

    Part 2 of this series can be found Here

    With the hardware to read the PAL "brute force", all we need is a program to do it.

    //	Read a 10L8 PAL and come up with a truth table.
    //		Uses the little board with the 393s
    #include <stdlib.h>
    #include <stdio.h>
    #include <dos.h>
    #define PRINTER 0x378			// printer base port
    #define PAL_DATA 0x80			// bit representing the

    Updated October 3rd, 2011 at 06:43 PM by Chuck(G)

  2. Cloning a PAL/HAL (Part 2)

    Part 1 of this blog post can be found here.

    So, basically, the problem boils down to the problem of having a black box with 10 inputs and 8 outputs and having to figure out what's inside. We do know that it's simple combinatorial logic and there's no memory inside. Furthermore, none of the outputs are fed back internally to the inputs, all of which greatly simplifies our task.

    All we have to do is present every possible combination of the 10 inputs (all 1,024 of them) ...

    Updated October 3rd, 2011 at 06:41 PM by Chuck(G)

  3. Cloning a PAL/HAL (Part 1)

    I'll be posting this in pieces because I want to take the time to make it understandable.

    So, what's a PAL?

    PAL stands for Programmable Array Logic and is a type of integrated circuit that consists some simple logic that can be connected via a programming procedure, much like a PROM. Connections are made by "fuses" in a metal overlay that can be "blown" by a device programmer.

    A variation of the PAL is the "HAL", which is ...

    Updated October 3rd, 2011 at 06:39 PM by Chuck(G)

  4. Modifying an IBM 4869 external floppy box, Part 2

    Okay, now replace the cable retainer (all plastic), making sure to press firmly along its entire length to make sure that all wires have been pierced by the insulation-displacing contacts and that the retainer latches into the connector body:
    Attachment 3666

    Fold the cable over the connector body as it was originally, and replace the strain relief. You may need to bend the ears slightly together to get the relief to latch over the retainer. You'll probably have a bit ...
  5. Modifying an IBM 4869 external floppy box to work with a 5150

    ...or any other standard floppy controller with an external drive connector (it works fine on a Compaticard, for example).

    First, take your 4869 apart. Note that there are 8 screws on the bottom and that 2 of these are tamper-proof Torx-head screws. Fortunately, it's easy to find screwdriver bits for these tamper-proof screws, which makes them not so tamper-proof. Note which holes belong to which screws. The Torx head screws are longer than the others and will enlarge the other ...
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