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View Diary: Top Comments: The Town That Mapmakers "Built" (49 comments)

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  •  Back in the day (1+ / 0-)
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    When wiring up an early homebrew PC, shortly after chips appeared that would take ASCII bytes in on the data lines and display them as characters on a screen, I had the Bright Idea of treating that as WOM.

    We had 16 address lines and a 64K address space.

    So I figured, wire the board so that E000-E3FF would read from the PROM, but write to the video controller.  You couldn't write to the PROM, and why read from the video chip?  Elegant, no?

    Actually it turned out to be useful to read from the video chip, so you could (for example) copy Line 6 up to Line 5 when scrolling.  If you couldn't, you had to keep a copy in memory, defeating the whole purpose.

    It was quicker to wirewrap than to think these things through...

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