removed faulty JiffyDOS optimization (compatibility problems)

c64/kernal/iec/iec_tx_command.s

@@ -16,6 +16,22 @@ iec_tx_command:
 	phx_trash_a
 	phy_trash_a
 
+#if CONFIG_IEC_JIFFYDOS
+
+	// IMHO detecting JiffDOS would be sufficient for TALK and LISTEN commands,
+	// this would also make the protocol slightly faster. But, for some reason
+	// (this is clearly visible in the logs) the original JiffyDOS Kernal tries
+	// to detect the JiffyDOS drive during each and every command - and trying
+	// to limit the detection to TALK/LISTEN only was causing transmission
+	// errors (at least with 1541 JiffyDOS ROM)
+
+	lda #$FF // force JiffyDOS detection
+	sta IECPROTO
+
+	// FALLTROUGH
+
+#endif // CONFIG_IEC_JIFFYDOS
+
 	// Notify all devices that we are going to send a byte
 	// and it is going to be a command (pulled ATN)
 	jsr iec_pull_atn_clk_release_data

c64/kernal/iec/talk.s

@@ -32,18 +32,6 @@ common_talk_listen: // common part of TALK and LISTEN
 
 	sta TBTCNT
 
-#if CONFIG_IEC_JIFFYDOS
-
-	// It seems that only TALK/LISTEN is used to detect the JiffyDOS support
-
-	lda #$FF // unknown protocol - check what is supported
-	sta IECPROTO
-
-	// FALLTROUGH
-
-#endif // CONFIG_IEC_JIFFYDOS
-
-
 	jmp iec_tx_command
 
 #else

c64/kernal/iec/unlsn.s

@@ -18,13 +18,6 @@ UNLSN:
 	// According to serial-bus.pdf (page 15) this routine flushes the IEC out buffer
 	jsr iec_tx_flush
 
-#if CONFIG_IEC_JIFFYDOS
-
-	lda #$00 // switch back to standard protocol
-	sta IECPROTO
-
-#endif
-
 	// Buffer empty, send the command
 	lda #$3F
 

c64/kernal/iec/untlk.s

@@ -18,13 +18,6 @@ UNTLK:
 	// According to serial-bus.pdf (page 15) this routine flushes the IEC out buffer
 	jsr iec_tx_flush
 
-#if CONFIG_IEC_JIFFYDOS
-
-	lda #$00 // switch back to standard protocol
-	sta IECPROTO
-
-#endif
-
 	// Buffer empty, send the command
 	lda #$5F