diff -urN linux.old/drivers/serial/8250.c linux.dev/drivers/serial/8250.c
--- linux.old/drivers/serial/8250.c	2006-06-08 20:21:20.000000000 +0200
+++ linux.dev/drivers/serial/8250.c	2006-06-08 20:19:40.000000000 +0200
@@ -351,6 +351,13 @@
 	default:
 		outb(value, up->port.iobase + offset);
 	}
+
+#if defined(CONFIG_IDT_EB434) || defined(CONFIG_MIKROTIK_RB500)
+	__SLOW_DOWN_IO;
+	__SLOW_DOWN_IO;
+	__SLOW_DOWN_IO;
+	__SLOW_DOWN_IO;
+#endif
 }
 
 /*

