diff -urNp x-ref/arch/i386/Makefile x/arch/i386/Makefile
--- x-ref/arch/i386/Makefile	2003-01-31 00:03:36.000000000 +0100
+++ x/arch/i386/Makefile	2003-01-31 00:21:29.000000000 +0100
@@ -51,11 +51,11 @@ CFLAGS += -march=i686
 endif
 
 ifdef CONFIG_MPENTIUMIII
-CFLAGS += -march=i686
+CFLAGS += $(shell if $(CC) -march=pentium3 -S -o /dev/null -xc /dev/null >/dev/null 2>&1; then echo "-march=pentium3"; else echo "-march=i686"; fi)
 endif
 
 ifdef CONFIG_MPENTIUM4
-CFLAGS += -march=i686
+CFLAGS += $(shell if $(CC) -march=pentium4 -S -o /dev/null -xc /dev/null >/dev/null 2>&1; then echo "-march=pentium4"; else echo "-march=i686"; fi)
 endif
 
 ifdef CONFIG_MK6
diff -urNp x-ref/include/asm-i386/prefetch.h x/include/asm-i386/prefetch.h
--- x-ref/include/asm-i386/prefetch.h	2003-01-31 00:03:27.000000000 +0100
+++ x/include/asm-i386/prefetch.h	2003-01-31 00:22:24.000000000 +0100
@@ -4,7 +4,7 @@
 #include <linux/config.h>
 
 /* Prefetch instructions for Pentium III and AMD Athlon */
-#ifdef 	CONFIG_MPENTIUMIII
+#if defined(CONFIG_MPENTIUMIII) || defined(CONFIG_MPENTIUM4)
 
 #define ARCH_HAS_PREFETCH
 extern inline void prefetch(const void *x)