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Thread: Amiga 1000 CIAs and fitting a boot selector

  1. #1
    MindWalker's Avatar
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    Default Amiga 1000 CIAs and fitting a boot selector

    Hi.

    I am doing a cleanup/recap/drive maintenance to my A1000. While there, I am hoping to install a DF0/DF1 selector (I found these a nice addition in my A500 with an exernal HxC drive). The internal drive in my A1000 is somewhat temperamental, not to mention very loud.

    My A1000 is an early PAL unit with the daughterboard. In this board, which one of the CIA chips is the one controlling the floppies, ie. to which the selector would attach to? On my board they are marked U6N and U6P.

    I have one more of these (https://www.ebay.co.uk/itm/283468629873) selectors which I used in my A500. If the correct CIA in A1000 is U6N (further from the 68000) it won't fit due to the daughterboard pins next to it. If it's the U6P it *might* fit there.

    In case the selector linked above won't fit, I guess I'll just build "the traditional" switch with stacked sockets and a switch to swap the required lines. I would have prefered the linked one due to the described "protection" to the CIAs but I guess the bare-bones switch method will work too.

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    Jack of Many Trades, Semi-Master of Some thebajaguy's Avatar
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    The SEL0/1 lines off the CIA are the pins that ultimately connect to the floppy, and the device is performing an effective DPDT switch on these two lines to reverse them.

    I believe it's the CIA closest to the 68000. I plan to do the same (DF0/DF1 swap), but I had to wait for the A1000 ribbon cable switcher (tuxbar81) to come in, and I have to re-research as I have forgotten. My non-ribbon version of the Kickstart switcher sat immediately over the CIAs. Plus an Insider 1000, plus an HC533...

    On the CIA, SEL0 is pin 13, SEL1 is pin 14, SEL 2 is pin 15, and SEL 3 is pin 16. SEL 0 / 1 / 2 / 3 on the internal cable header is pins 10 / 12 / 14 / 6 respectively. Page 2, right side, is the A1000 schematics here: archive.org/details/A1000_Board_Schematics_2008-05-31_-/page/n1 - just use a continuity meter. If you have the wrong CIA, it controls pins the parallel port.

    Edit: Deferring to MindWalker who completed the mod.
    Last edited by thebajaguy; 10th July 2019 at 02:00.
    A500(2x)/A1000/A1200/A2000(4x)/A3000D(2x)/A4000D(under repair)/A4000T (all loaded....Toys...Toys...Toys...)
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  3. #3
    MindWalker's Avatar
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    I just finished this mod. The correct CIA chip for the boot selector is U6N, which is further from the 68000, and just next to the daughterboard pins. The traditional stacked-socket selector fits there Ok, and I was able to mount a small switch inside the side-expansion slot's opening so it can be operated from the outside, and hopefully without interfering with the expansion slot's usage.

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