first commit

boot.s

@@ -0,0 +1,48 @@
+; Simple working bootblock
+    MACHINE 68000
+    ORG 0
+
+    dc.b    'D','O','S',0       ; DOS magic
+    dc.l    0                   ; Checksum
+    dc.l    880                 ; Rootblock
+
+; Boot code - a1=IORequest, a6=ExecBase
+boot_start:
+    ; Save IORequest pointer (PC-relative)
+    lea     SavedA1(pc),a0
+    move.l  a1,(a0)
+
+    ; Load game from disk
+    move.w  #2,28(a1)           ; CMD_READ
+    move.l  #$20000,40(a1)      ; io_Data
+    move.l  #11776,36(a1)       ; io_Length (Exact game size)
+    move.l  #1024,44(a1)        ; io_Offset
+    
+    jsr     -456(a6)            ; DoIO
+    
+    ; Check for Error
+    tst.l   d0
+    bne.s   .loadError
+
+    ; Restore IORequest pointer
+    lea     SavedA1(pc),a0
+    move.l  (a0),a1
+    
+    ; Turn off motor
+    move.w  #9,28(a1)           ; CMD_MOTOR
+    move.l  #0,36(a1)
+    jsr     -456(a6)            ; DoIO
+    
+    ; Jump to game
+    jmp     $20000
+
+.loadError:
+    ; Error: Magenta Screen Loop
+    move.w  #$F0F,$dff180
+    bra.s   .loadError
+
+SavedA1:
+    dc.l    0
+
+; Pad to 1024 bytes
+    dcb.b   1024-(*-0),0