diff -urN 2.4.5pre5/arch/alpha/kernel/core_tsunami.c 1G/arch/alpha/kernel/core_tsunami.c
--- 2.4.5pre5/arch/alpha/kernel/core_tsunami.c	Sun Apr  1 01:17:07 2001
+++ 1G/arch/alpha/kernel/core_tsunami.c	Wed May 23 05:00:11 2001
@@ -11,6 +11,7 @@
 #include <linux/pci.h>
 #include <linux/sched.h>
 #include <linux/init.h>
+#include <linux/bootmem.h>
 
 #include <asm/ptrace.h>
 #include <asm/system.h>
@@ -358,7 +359,13 @@
 	 * address range.
 	 */
 	hose->sg_isa = iommu_arena_new(hose, 0x00800000, 0x00800000, 0);
-	hose->sg_pci = iommu_arena_new(hose, 0xc0000000, 0x08000000, 0);
+	{
+		unsigned long size = 0x08000000;
+		if (max_low_pfn > (0x80000000 >> PAGE_SHIFT))
+			size = 0x40000000;
+		hose->sg_pci = iommu_arena_new(hose, 0xc0000000, size, 0);
+	}
+	
 	__direct_map_base = 0x40000000;
 	__direct_map_size = 0x80000000;