diff --git a/lib_ppc/board.c b/lib_ppc/board.c
index ee0213e..3ab22f8 100644
--- a/lib_ppc/board.c
+++ b/lib_ppc/board.c
@@ -433,7 +433,18 @@
 	 */
 	len = (ulong)&_end - CFG_MONITOR_BASE;
 
+#ifndef CONFIG_MAX_MEM_MAPPED
+#define CONFIG_MAX_MEM_MAPPED (256 << 20)
+#endif
+
+#ifndef	CONFIG_VERY_BIG_RAM
 	addr = CFG_SDRAM_BASE + get_effective_memsize();
+#else
+	/* only allow stack below 256M */
+	addr = CFG_SDRAM_BASE +
+		(gd->ram_size > CONFIG_MAX_MEM_MAPPED) ?
+		CONFIG_MAX_MEM_MAPPED : get_effective_memsize();
+#endif
 
 #ifdef CONFIG_LOGBUFFER
 #ifndef CONFIG_ALT_LB_ADDR