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rom4x
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Update README.md

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mgcaret 2017-03-16 20:12:41 -07:00 committed by GitHub
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@ -2,6 +2,9 @@
## PRELIMINARY, NOT EXTENSIVELY TESTED
*I have not tested this with the A2Heaven RAM card yet, but all of the other
functionality definitely works.
This is ROM 5X, providing the ROM 4X functionality to the Apple IIc Plus ROM
version 5.
@ -16,11 +19,13 @@ presumably so that multiple beeps are distinct from each other.
I patch the JSR WAIT to be STA $C028, which switches to the other bank.
The code in the other bank checks the accumulator and for two values calls
either reset5x or boot5x, and for any other value executes the WAIT (assuming
that we got there from BEEP1) and returns back to BEEP1.
either reset5x or boot5x, for a third value ($40 loaded by BEEP1) does the
classic Apple II "air raid" beep sound, and for any other value executes the WAIT
(assuming that we got there from BEEP1) and returns back to BEEP1.
Then, in only 6 bytes I can create two entry points that load the value into
A that we need for the reset or boot routines, and then jump to the above patch.
Then, in only 6 bytes I can create two entry points that load the right values
into the A register that we need for the reset or boot routines, and then jump
to the above patch.
## Options