diff -uNr linux-2.6.10/arch/x86_64/kernel/io_apic.c linux-2.6.10.new.x86_64/arch/x86_64/kernel/io_apic.c
--- linux-2.6.10/arch/x86_64/kernel/io_apic.c	2004-12-24 13:34:45.000000000 -0800
+++ linux-2.6.10.new.x86_64/arch/x86_64/kernel/io_apic.c	2004-12-28 15:46:35.828076192 -0800
@@ -1148,6 +1148,19 @@
 	unsigned char old_id;
 	unsigned long flags;
 
+        unsigned int max_apic;
+        u32 vendor;
+
+        /* get the max apic */
+        vendor = read_pci_config(0, 0x18, 0, PCI_VENDOR_ID);
+        vendor &= 0xffff;
+        if(vendor == PCI_VENDOR_ID_AMD) { /* AMD */
+                max_apic = (((read_pci_config(0, 0x18, 0, 0x68)>>17) & 3) == 3) ? 0xff : 0xf;
+        }
+        else { /* intel:  how to find out if intel em64t support 256 apic id? */
+                max_apic = 0xf;
+        }
+
 	/*
 	 * Set the IOAPIC ID to the value stored in the MPC table.
 	 */
@@ -1160,7 +1173,7 @@
 		
 		old_id = mp_ioapics[apic].mpc_apicid;
 
-		if (mp_ioapics[apic].mpc_apicid >= 0xf) {
+		if (mp_ioapics[apic].mpc_apicid >= max_apic) {
 			apic_printk(APIC_QUIET,KERN_ERR "BIOS bug, IO-APIC#%d ID is %d in the MPC table!...\n",
 				apic, mp_ioapics[apic].mpc_apicid);
 			apic_printk(APIC_QUIET,KERN_ERR "... fixing up to %d. (tell your hw vendor)\n",