From 38135f293b3b3624f6624981569f89a86300ffba Mon Sep 17 00:00:00 2001
From: Fred Sauer <fredsa@google.com>
Date: Thu, 3 Sep 2026 22:19:49 -0700
Subject: [PATCH] apple2: allow arbitrary start addresses for DOS 3.3 binaries

Remove requirement for start address to be $0803 or multiple of 256
---
 presets/apple2/dos33bin.a | 2 +-
 src/machine/apple2.ts     | 3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/presets/apple2/dos33bin.a b/presets/apple2/dos33bin.a
index fb52ed75..40afabd2 100644
--- a/presets/apple2/dos33bin.a
+++ b/presets/apple2/dos33bin.a
@@ -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
diff --git a/src/machine/apple2.ts b/src/machine/apple2.ts
index 504fa7d1..e390ced5 100644
--- a/src/machine/apple2.ts
+++ b/src/machine/apple2.ts
@@ -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;