diff -urN highmemdebug-ref/arch/i386/config.in highmemdebug/arch/i386/config.in
--- highmemdebug-ref/arch/i386/config.in	Wed Feb 20 00:26:25 2002
+++ highmemdebug/arch/i386/config.in	Wed Feb 20 00:27:21 2002
@@ -436,6 +436,9 @@
    bool '  Magic SysRq key' CONFIG_MAGIC_SYSRQ
    bool '  Spinlock debugging' CONFIG_DEBUG_SPINLOCK
    bool '  Verbose BUG() reporting (adds 70K)' CONFIG_DEBUG_BUGVERBOSE
+   if [ "$CONFIG_HIGHMEM" = "y" ]; then
+      bool '  Emulate HIGHMEM on lowmem machines' CONFIG_HIGHMEM_EMULATION
+   fi
 fi
 
 endmenu
diff -urN highmemdebug-ref/arch/i386/kernel/setup.c highmemdebug/arch/i386/kernel/setup.c
--- highmemdebug-ref/arch/i386/kernel/setup.c	Wed Feb 20 00:26:13 2002
+++ highmemdebug/arch/i386/kernel/setup.c	Wed Feb 20 00:26:54 2002
@@ -835,7 +835,20 @@
 /*
  * Reserved space for vmalloc and iomap - defined in asm/page.h
  */
+#ifdef CONFIG_HIGHMEM_EMULATION
+#define ORDER_DOWN(x)	((x >> (MAX_ORDER-1)) << (MAX_ORDER-1))
+#define MAXMEM_PFN					\
+({							\
+	int __max_pfn;					\
+	if (max_pfn > PFN_DOWN(MAXMEM))			\
+	     __max_pfn = PFN_DOWN(MAXMEM);		\
+	else						\
+	     __max_pfn = ORDER_DOWN(max_pfn / 5);	\
+	__max_pfn;					\
+})
+#else
 #define MAXMEM_PFN	PFN_DOWN(MAXMEM)
+#endif
 #define MAX_NONPAE_PFN	(1 << 20)
 
 	/*