A500 mobo 8a1 ram question

Deling

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I have 8a1 mobo A500+ with 512kb , I want upgrade this machine to 1mb chip or 2 mb chip direct to mobo
there is 8375 agnus , what I have to do ? looking for good solution
 

BLTCON0

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For 1 MB chip RAM onboard, you simply convert the board to A500+ specs (alter some jumpers, add an IC, install missing RAM chips). Then it can be upgraded to 2 MB chip RAM via a 1 MB trapdoor expansion.

For 2 MB chip RAM onboard, forget it. Only the "good" revision, rev6A (and its lost identical twin, the rev7), can be "cleanly" upgraded to 2 MB chip RAM onboard. You can of course do it on the rev8 as well, but it requires stuff like piggybacking another set of 8 RAM chips on top of the existing 8 ones and routing the 8375 Agnus' secondary (trapdoor) RAS lines there. Not a clean solution, and the added elevation caused by piggybacking the chips may well interfere with the shielding and/or the keyboard (which is known to bend downwards at the center).
 

Sardine

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IC = Integrated Circuit.. or chip.
 
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