Index: head/sys/dev/ic/z8530.h
===================================================================
--- head/sys/dev/ic/z8530.h
+++ head/sys/dev/ic/z8530.h
@@ -32,15 +32,14 @@
 #define	_DEV_IC_Z8530_H_
 
 /*
- * Channel B control:	0
- * Channel B data:	1
- * Channel A control:	2
- * Channel A data:	3
+ * legacy:	SUN compatible
+ * escc: 	Macintosh
+ *			legacy		escc
+ * Channel B control:	0		0
+ * Channel B data:	1		1
+ * Channel A control:	2		16
+ * Channel A data:	3		17
  */
-
-/* The following apply when using a device-scoped bus handle */
-#define	CHAN_A		2
-#define	CHAN_B		0
 
 #define	REG_CTRL	0
 #define	REG_DATA	1
Index: head/sys/dev/scc/scc_bfe.h
===================================================================
--- head/sys/dev/scc/scc_bfe.h
+++ head/sys/dev/scc/scc_bfe.h
@@ -114,7 +114,8 @@
 
 extern struct scc_class scc_quicc_class;
 extern struct scc_class scc_sab82532_class;
-extern struct scc_class scc_z8530_class;
+extern struct scc_class scc_z8530_escc_class;
+extern struct scc_class scc_z8530_legacy_class;
 
 struct scc_softc {
 	KOBJ_FIELDS;
Index: head/sys/dev/scc/scc_bfe_macio.c
===================================================================
--- head/sys/dev/scc/scc_bfe_macio.c
+++ head/sys/dev/scc/scc_bfe_macio.c
@@ -55,9 +55,10 @@
 
 	sc = device_get_softc(dev);
 	nm = ofw_bus_get_name(dev);
+	/* Attach to modern escc (channel shift 4 bits) */
 	if (!strcmp(nm, "escc")) {
 		device_set_desc(dev, "Zilog Z8530 dual channel SCC");
-		sc->sc_class = &scc_z8530_class;
+		sc->sc_class = &scc_z8530_escc_class;
 		return (scc_bfe_probe(dev, MACIO_REGSHFT, MACIO_RCLK, 0));
 	}
 	return (ENXIO);
Index: head/sys/dev/scc/scc_dev_z8530.c
===================================================================
--- head/sys/dev/scc/scc_dev_z8530.c
+++ head/sys/dev/scc/scc_dev_z8530.c
@@ -51,6 +51,10 @@
 static int z8530_bfe_ipend(struct scc_softc *);
 static int z8530_bfe_probe(struct scc_softc *);
 
+/* Channel B is always at 0 offset. */
+#define	CHAN_A	(-(sc->sc_class->cl_range))
+#define	CHAN_B	0
+
 static kobj_method_t z8530_methods[] = {
 	KOBJMETHOD(scc_attach,	z8530_bfe_attach),
 	KOBJMETHOD(scc_iclear,	z8530_bfe_iclear),
@@ -59,14 +63,32 @@
 	KOBJMETHOD_END
 };
 
-struct scc_class scc_z8530_class = {
-	"z8530 class",
+/*
+ * escc (macio) spacing.
+ */
+struct scc_class scc_z8530_escc_class = {
+	"z8530 escc class",
 	z8530_methods,
 	sizeof(struct scc_softc),
 	.cl_channels = 2,
 	.cl_class = SCC_CLASS_Z8530,
 	.cl_modes = SCC_MODE_ASYNC | SCC_MODE_BISYNC | SCC_MODE_HDLC,
-	.cl_range = CHAN_B - CHAN_A,
+	/* Negative .cl_range signifies this is channel spacing. */
+	.cl_range = (CHAN_B - 16),
+};
+
+/*
+ * SUN compatible channel spacing.
+ */
+struct scc_class scc_z8530_legacy_class = {
+	"z8530 legacy class",
+	z8530_methods,
+	sizeof(struct scc_softc),
+	.cl_channels = 2,
+	.cl_class = SCC_CLASS_Z8530,
+	.cl_modes = SCC_MODE_ASYNC | SCC_MODE_BISYNC | SCC_MODE_HDLC,
+	/* Negative .cl_range signifies this is channel spacing. */
+	.cl_range = (CHAN_B - 2),
 };
 
 /* Multiplexed I/O. */