adapted SID initialization for these insane 8 SID configurations

STATUS.md

@@ -6,7 +6,7 @@ Here are the features of the Open ROMs not found in the original ROMs from the 8
 * improved keyboard scanning, supports multi-key roll-over and rejection of spurious joystick input
 * joystick (port 1) can be used to move text cursor
 * uses RAM under ROM and I/O: 61436 bytes free
-* cold/warm start silences SID chips - $D400, $D420, ..., $D4E0, $D500 
+* cold/warm start silences multiple SID chips - all $D4xx and $D5xx addresses
 * extended `LOAD` command
     * start/end addresses are displayed, in the Final cartridge style
     * command with just the file name tries to use the last device if it's number seems sane; otherwise uses 8

c64/kernal/fda3.ioinit.s

@@ -20,25 +20,24 @@ ioinit:
 	sta CPU_R6510
 	stx CPU_D6510
 
-	;; Silence the SID chips in the $D4xx range
+	;; Silence the SID chips under common addresses
 
 	ldy #$00
 *
+	;; SIDs under $D4xx
 	lda SID_SIGVOL, Y
 	and #$F0
 	sta SID_SIGVOL, Y
+	;; SIDs under $D5xx
+	lda SID_SIGVOL + $100, Y
+	and #$F0
+	sta SID_SIGVOL + $100, Y
 	tya
 	clc
 	adc #$20
 	tay
 	bne -
 
-	;; Silence the SID chip on $D500
-
-	lda SID_SIGVOL+$100
-	and #$F0
-	sta SID_SIGVOL+$100
-
 	;; XXX: calibrate TOD for both CIA's, see here: https://codebase64.org/doku.php?id=base:efficient_tod_initialisation
 
 	;; Enable CIA1 IRQ and ~50Hz timer (https://csdb.dk/forums/?roomid=11&topicid=69037)