Index: conf/options.mips
===================================================================
--- conf/options.mips	(revision 240075)
+++ conf/options.mips	(working copy)
@@ -82,6 +82,7 @@
 AR71XX_ENV_UBOOT		opt_ar71xx.h
 AR71XX_ENV_REDBOOT		opt_ar71xx.h
 AR71XX_ATH_EEPROM		opt_ar71xx.h
+AR71XX_ROUTERBOOT		opt_ar71xx.h
 
 #
 # Options that control the Ralink RT305xF Etherenet MAC.
Index: mips/atheros/ar71xx_machdep.c
===================================================================
--- mips/atheros/ar71xx_machdep.c	(revision 239916)
+++ mips/atheros/ar71xx_machdep.c	(working copy)
@@ -140,6 +140,30 @@
 	}
 }
 
+#ifdef	AR71XX_ROUTERBOOT
+/*
+ * Parse the available boad memory from command line arguments.
+ */
+static int
+ar71xx_routerboot_get_mem(int argc, char **argv)
+{
+	int i, board_mem;
+
+	/* 
+	 * Protect ourselves from garbage in registers 
+	 */
+	if (MIPS_IS_VALID_PTR(argv)) {
+		for (i = 0; i < argc; i++) {
+			if (strncmp(argv[i], "mem=", 4) == 0) {
+				if (sscanf(argv[i] + 4, "%dM", &board_mem) == 1)
+					return (btoc(board_mem * 1024 * 1024));
+			}
+		}
+	}
+	return (0);
+}
+#endif
+
 void
 platform_start(__register_t a0 __unused, __register_t a1 __unused, 
     __register_t a2 __unused, __register_t a3 __unused)
@@ -183,7 +207,15 @@
 		}
 	}
 
+#ifdef	AR71XX_ROUTERBOOT
 	/*
+	 * RouterBoot informs the board memory as a command line argument.
+	 */
+	if (realmem == 0)
+		realmem = ar71xx_routerboot_get_mem(argc, argv);
+#endif
+
+	/*
 	 * Just wild guess. RedBoot let us down and didn't reported 
 	 * memory size
 	 */
Index: mips/atheros/if_arge.c
===================================================================
--- mips/atheros/if_arge.c	(revision 239916)
+++ mips/atheros/if_arge.c	(working copy)
@@ -36,6 +36,7 @@
 #endif
 
 #include "opt_arge.h"
+#include "opt_ar71xx.h"
 
 #include <sys/param.h>
 #include <sys/endian.h>
@@ -371,6 +370,9 @@
 	uint32_t		hint;
 	long			eeprom_mac_addr = 0;
 	int			miicfg = 0;
+#ifdef	AR71XX_ROUTERBOOT
+	char			*board;
+#endif
 
 	sc = device_get_softc(dev);
 	sc->arge_dev = dev;
@@ -533,8 +535,21 @@
 		sc->arge_eaddr[4] = (rnd >> 16) & 0xff;
 		sc->arge_eaddr[5] = (rnd >> 8) & 0xff;
 	}
-	if (sc->arge_mac_unit != 0)
-		sc->arge_eaddr[5] +=  sc->arge_mac_unit;
+#ifdef	AR71XX_ROUTERBOOT
+	/*
+	 * Some RouterBoards (RB433x, RB450x and RB493x) uses the unit 1 as
+	 * main (WAN) port.  Invert the mac address setup logic if needed.
+	 */
+	if ((board = getenv("board")) != NULL &&
+	    (strncmp(board, "433", 3) == 0 ||
+	     strncmp(board, "450", 3) == 0 ||
+	     strncmp(board, "493", 3) == 0)) {
+		if (sc->arge_mac_unit == 0)
+			sc->arge_eaddr[5] += 1;
+	} else
+#endif
+		if (sc->arge_mac_unit != 0)
+			sc->arge_eaddr[5] += sc->arge_mac_unit;
 
 	if (arge_dma_alloc(sc) != 0) {
 		error = ENXIO;