diff -r 2e6a51378451 xen/arch/x86/cpu/amd.c
--- a/xen/arch/x86/cpu/amd.c	Thu May 22 15:11:06 2008 +0100
+++ b/xen/arch/x86/cpu/amd.c	Fri May 23 10:42:31 2008 +0200
@@ -74,9 +74,11 @@ static void disable_c1_ramping(void)
 static void disable_c1_ramping(void) 
 {
 	u8 pmm7;
-	int node;
-
-	for (node=0; node < NR_CPUS; node++) {
+	int node, nr_nodes;
+
+	/* read the number of nodes from the first northbridge */
+	nr_nodes = ((pci_conf_read32(0, 0x18, 0x0, 0x60)>>4)&0x07)+1;
+	for (node=0; node < nr_nodes; node++) {
 		/* PMM7: bus=0, dev=0x18+node, function=0x3, register=0x87. */
 		pmm7 = pci_conf_read8(0, 0x18+node, 0x3, 0x87);
 		/* Invalid read means we've updated every Northbridge. */