--- linux-2.6.12-RT-51-31/arch/i386/kernel/io_apic.c	2005-07-17 12:40:35.000000000 +0200
+++ linux-2.6.12-RT/arch/i386/kernel/io_apic.c	2005-07-17 13:33:06.000000000 +0200
@@ -158,7 +158,7 @@
 static void __init ioapic_cache_init(struct ioapic_data_struct *ioapic)
 {
 	int reg;
-	for (reg = 0; reg < (ioapic->nr_registers + 10); reg++)
+	for (reg = 0; reg < (0x10 + 2 * ioapic->nr_registers); reg++)
 		ioapic->cached_val[reg] = __raw_io_apic_read(ioapic, reg);
 }
 # endif