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articles:iicplus_merlin [2017/12/14 15:10] M.G. [Fixing ROM 5X] |
articles:iicplus_merlin [2017/12/14 15:13] M.G. [Fixing ROM 5X] |
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| While there are other miscellaneous changes and code reorganizations around fixing this problem (they can be seen in the [[https://github.com/mgcaret/rom4x/commit/d5969104cdca6fb3746e47080364c6deb2874f7b|commit]]), they are not centrally important to the problem we are fixing. | While there are other miscellaneous changes and code reorganizations around fixing this problem (they can be seen in the [[https://github.com/mgcaret/rom4x/commit/d5969104cdca6fb3746e47080364c6deb2874f7b|commit]]), they are not centrally important to the problem we are fixing. | ||
| - | The main parts of the fix are as follows: | + | The main parts of the fix are as follows: (Important note: The ROM in $Cxxx is //always visible// no matter what, there's no way to switch it out for RAM.) |
| Move the dispatcher bank switch out of the BELL1 routine to a few free bytes at $C7FC in the main bank and $C7FF of the aux bank: | Move the dispatcher bank switch out of the BELL1 routine to a few free bytes at $C7FC in the main bank and $C7FF of the aux bank: | ||
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| </code> | </code> | ||
| - | We make use of the IIc Plus's existing routines to save and restore the language card state, and in between we call the ROM 5X dispatch, which executes the classic "air raid beep" that the Apple II line is known for. | + | We make use of the IIc Plus's existing routines to save and restore the language card state, and in between we call the ROM 5X dispatch, which executes the classic "air raid beep" that the Apple II line is known for. In fact, this can be used to call any of the ROM 5X functions, now or in the future, and preserve the RAM state, provided we don't care about the contents of the A register. |