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apple2: allow arbitrary start addresses for DOS 3.3 binaries #264

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Merged
sehugg merged 1 commit into from
Sep 6, 2026
Merged

apple2: allow arbitrary start addresses for DOS 3.3 binaries #264

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2 changes: 1 addition & 1 deletion presets/apple2/dos33bin.a
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@
; --------------------------------------------------
; Set PGM_START to desired start of program execution
; - PGM_START must be less than $C000
; - PGM_START + SIZE must be less than $13000
; - PGM_START + PGM_LENGTH must be less than $13000
; --------------------------------------------------
PGM_START equ $2000
PGM_LENGTH equ PGM_END - PGM_START
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3 changes: 1 addition & 2 deletions src/machine/apple2.ts
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Expand Up @@ -195,8 +195,7 @@ export class AppleII extends BasicScanlineMachine implements AcceptsBIOS, Accept
const hdrOrigin = this.rom[0] | (this.rom[1] << 8);
const size = this.rom[2] | (this.rom[3] << 8);
let isPlausible = hdrOrigin < 0xc000
&& hdrOrigin + size < 0x13000
&& (hdrOrigin == 0x803 || (hdrOrigin & 0xff) == 0);
&& hdrOrigin + size < 0x13000;
if (size == data.length - 4 && isPlausible) {
this.LOAD_BASE = hdrOrigin;
this.HDR_SIZE = 4;
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