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Thread: Amiga 500 rev 5 - 2MB chip possible?

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    Question Amiga 500 rev 5 - 2MB chip possible?

    I've asked this over at English Amiga Board, but I'm anxious to know if this will work, so I'll repeat post here in the hope of catching an answer faster

    Quote Originally Posted by arnljot
    I have a MegaChip (under way), Agnus 2MB pal (8375 390544-01).


    And I have under way 30 nec dram chips 100ns, suitable for install on an a500 MB.


    Could I combine this to make the A500 rev 5 have 2MB chip?


    https://myoldcomputer.nl/amiga/1-mb-...am-a500-rev-5/

    https://acillclassics.wordpress.com/...-a500-install/

    http://www.amibay.com/showthread.php...000-CDTV-30%80



    The 1MB mod requires to isolate out pin 41 of the Agnus 8372a used in the 1MB mod.


    The megachip mod just attaches to the gary at it's pin 36.


    Can these two mods be combined, and can I ignore the agnus pin mod on the 1MB mod?


    PS, for the 1MB in the trapdoor Im thinking the A314
    Been away for a long time, time for comeback?

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    Hi arnljot

    I've successfully upgraded a rev5 to 2Meg Chipram with no problems using the kit available here on Amibay

    It requires some heavy soldering though but you are welcome to send me the board and kit and I will do it for you just for postage
    Ritchie Blackmore's Rainbow June 2016, I Was There

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    I have DjCook's MegaChip 2MB on my Rev. 5. I would recommend using trapdoor RAM instead of piggybacking the DRAM, because the extra height could interfere with the bottom of the keyboard (though maybe this only happens with Rev. 6A?).

    Also, I know of a nicer place to drop the A20 wire instead of tacking it to Gary, which I personally find pretty shoddy (and anyway I had to replace Gary.) There's a via you can simply solder a pin down into.

    Click image for larger version. 

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    Quote Originally Posted by TheCorfiot View Post
    you are welcome to send me the board and kit and I will do it for you just for postage
    Thank you so much for your kind offer, how ever my son is a soldering padwan. He's been working as an apple repair tech, and has had training during he's education. But he's slow on the trigger to get it done, so I guess I wont save much time compared to shipping it out to you, but I'll at least save the shipping cost

    Quote Originally Posted by rmzalbar View Post
    II would recommend using trapdoor RAM instead of piggybacking the DRAM, because the extra height could interfere with the bottom of the keyboard (though maybe this only happens with Rev. 6A?).
    Interesting point.

    Quote Originally Posted by rmzalbar View Post
    I know of a nicer place to drop the A20 wire instead of tacking it to Gary, which I personally find pretty shoddy (and anyway I had to replace Gary.) There's a via you can simply solder a pin down into.
    Is it the via above the zero of the EM1702 label? Due to the isolation on the jump wire it was hard to make out where it landed.

    Option #1
    I'll let the A314 add 512k chip ram via the trap door.. It'l configure the jumpers so that it's a 512K memory board then.
    The MegaChip I bought ages ago from tbtorro will add an 8375 agnus and 1MB chip.
    The remaining 512k chip is provided by the rev5 motherboard.
    PRO:
    - No ram soldering on motherboard
    - Avoid possible conflict with keyboard due to ram height
    CON:
    - MegaChip might conflict with other expansions (accellerators, scan doubler, etc)

    Option #2
    Add 512k chip to the motherboard via this mod (solder another 512k on top of existing RAM).
    Add the A314 as a 1MB chip ram board via it's jumper configuration.
    Mod the rev5 to take a 8375 agnus via this mod.
    PRO:
    - Cheaper, doesn't "consume" the MegaChip. Leaves it free for my other machine. Also more spacious inside.
    - Maybe more compatible with A314, "behaves like 500+" to it?
    CON:
    - Keyboard conflict
    - More work on mother board, more risk


    Any options I've over looked?
    Been away for a long time, time for comeback?

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