--- linux/arch/i386/kernel/apic.c	2003-10-25 11:44:59.000000000 -0700
+++ linux-jla/arch/i386/kernel/apic.c	2003-12-09 19:07:19.000000000 -0700
@@ -1089,6 +1089,16 @@
 	 */
 	irq_stat[cpu].apic_timer_irqs++;
 
+#ifdef CONFIG_MK7 && CONFIG_BLK_DEV_AMD74XX
+
+	/*
+	 * on 2200XP & nforce2 chipset we need at least 500ns delay here
+	 * to stop lockups with udma100 drive. try to scale delay time
+	 * with cpu speed. Ross Dickson.
+	 */
+	ndelay((cpu_khz >> 12)+200 ); /* don't ack too soon or hard lockup */
+#endif
+
 	/*
 	 * NOTE! We'd better ACK the irq immediately,
 	 * because timer handling can be slow.