GM813 - Z80A / 64K RAM Card
This board supported an improved memory mapping architecture. It allows any 4K block to be mapped to any 4K boundary. Using the extended address lines A16..A19, the memory could be expanded to 1MB. Strangely address line A19 was never brought out to the bus giving only 512K actually addressable. This caused confusion later on as MAP systems and Gemini chose different unused 80-BUS lines for A19.
Technical Details
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