diff --git a/sys/uvm/uvm_readahead.c b/sys/uvm/uvm_readahead.c
index 68efb02bab0f..1154e2e367cc 100644
--- a/sys/uvm/uvm_readahead.c
+++ b/sys/uvm/uvm_readahead.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: uvm_readahead.c,v 1.3 2007/03/12 18:18:39 ad Exp $	*/
+/*	$NetBSD: uvm_readahead.c,v 1.4 2007/05/11 12:11:09 tsutsui Exp $	*/
 
 /*-
  * Copyright (c)2003, 2005 YAMAMOTO Takashi,
@@ -40,7 +40,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_readahead.c,v 1.3 2007/03/12 18:18:39 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_readahead.c,v 1.4 2007/05/11 12:11:09 tsutsui Exp $");
 
 #include <sys/param.h>
 #include <sys/pool.h>
@@ -66,6 +66,12 @@ struct uvm_ractx {
 	off_t ra_next;		/* next offset to read-ahead */
 };
 
+#if defined(sun2) || (defined(sun3) && defined(_SUN3_))
+/* XXX: on sun2 and sun3 (but not sun3x) MAXPHYS is 0xe000 */
+#undef MAXPHYS	
+#define MAXPHYS		0x8000	/* XXX */
+#endif
+
 #define	RA_WINSIZE_INIT	MAXPHYS			/* initial window size */
 #define	RA_WINSIZE_MAX	(MAXPHYS * 8)		/* max window size */
 #define	RA_WINSIZE_SEQENTIAL	RA_WINSIZE_MAX	/* fixed window size used for