diff -urN ref/arch/alpha/kernel/core_tsunami.c 2.4.5pre4aa1/arch/alpha/kernel/core_tsunami.c
--- ref/arch/alpha/kernel/core_tsunami.c	Tue May 22 18:22:38 2001
+++ 2.4.5pre4aa1/arch/alpha/kernel/core_tsunami.c	Tue May 22 18:21:09 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>
@@ -367,7 +368,8 @@
 	 * address range.
 	 */
 	hose->sg_isa = iommu_arena_new(hose, 0x00800000, 0x00800000, 0);
-	hose->sg_pci = iommu_arena_new(hose, 0xc0000000, 0x08000000, 0);
+	hose->sg_pci = iommu_arena_new(hose, 0xc0000000, 0x40000000, 0);
+	
 	__direct_map_base = 0x40000000;
 	__direct_map_size = 0x80000000;
 
@@ -383,9 +385,12 @@
 	pchip->wsm[2].csr  = (0x40000000 - 1) & 0xfff00000;
 	pchip->tba[2].csr  = 0x40000000;
 
-	pchip->wsba[3].csr = hose->sg_pci->dma_base | 3;
-	pchip->wsm[3].csr  = (hose->sg_pci->size - 1) & 0xfff00000;
-	pchip->tba[3].csr  = virt_to_phys(hose->sg_pci->ptes);
+	if (max_low_pfn > (0x80000000 >> PAGE_SHIFT)) {
+		pchip->wsba[3].csr = hose->sg_pci->dma_base | 3;
+		pchip->wsm[3].csr  = (hose->sg_pci->size - 1) & 0xfff00000;
+		pchip->tba[3].csr  = virt_to_phys(hose->sg_pci->ptes);
+	} else
+		pchip->wsba[3].csr = 0;
 
 	tsunami_pci_tbi(hose, 0, -1);