diff -urN linux-2.4.20/arch/i386/kernel/io_apic.c linux-2.4.20/arch/i386/kernel/io_apic.c
--- linux-2.4.20/arch/i386/kernel/io_apic.c	Thu Jan  2 17:56:34 2003
+++ linux/arch/i386/kernel/io_apic.c	Thu Jan  2 17:54:20 2003
@@ -264,7 +264,7 @@
 		allowed_mask = cpu_online_map & irq_affinity[irq];
 		entry->timestamp = now;
 		entry->cpu = move(entry->cpu, allowed_mask, now, random_number);
-		set_ioapic_affinity(irq, cpu_present_to_apicid(entry->cpu));
+		set_ioapic_affinity(irq, apicid_to_phys_cpu_present(entry->cpu));
 	}
 #endif
 }