diff --git a/sys/arch/mips/mips/mips_mcclock.c b/sys/arch/mips/mips/mips_mcclock.c
index 4ca29fe92568..373ec2c065d4 100644
--- a/sys/arch/mips/mips/mips_mcclock.c
+++ b/sys/arch/mips/mips/mips_mcclock.c
@@ -1,4 +1,4 @@
-/* $NetBSD: mips_mcclock.c,v 1.11 2002/03/05 15:54:33 simonb Exp $ */
+/* $NetBSD: mips_mcclock.c,v 1.12 2005/01/01 09:48:39 simonb Exp $ */
 
 /*
  * Copyright (c) 1997 Jonathan Stone (hereinafter referred to as the author)
@@ -34,7 +34,7 @@
 
 #include <sys/cdefs.h>			/* RCS ID & Copyright macro defns */
 
-__KERNEL_RCSID(0, "$NetBSD: mips_mcclock.c,v 1.11 2002/03/05 15:54:33 simonb Exp $");
+__KERNEL_RCSID(0, "$NetBSD: mips_mcclock.c,v 1.12 2005/01/01 09:48:39 simonb Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -146,7 +146,7 @@ mips_mcclock_tickloop(mcclock_addr, clockmask)
 	void *mcclock_addr;
 	int clockmask;
 {
-	int iters = 0;
+	int iters;
 	volatile int junk;
 	volatile struct mcclock_pad32_clockdatum *clk = mcclock_addr;
 
@@ -164,19 +164,12 @@ mips_mcclock_tickloop(mcclock_addr, clockmask)
 	junk++;	junk++;	junk++;	junk++;
 
 	/* Count loops until next tick-interrupt request occurs (4ms). */
-	if (MIPS_HAS_CLOCK) {
-		while ((mips_cp0_cause_read() & clockmask) == 0) {
-			__asm __volatile ("nop; nop; nop; nop");
-			iters++;
-		}
-	} else {
-		while ((mips_cp0_cause_read() & clockmask) == 0) {
-			__asm __volatile ("nop; nop;");
-			iters++;
-		}
-	}
+	if (MIPS_HAS_CLOCK)
+		iters = mips_mcclock_loop_with_clock(clockmask);
+	else
+		iters = mips_mcclock_loop_without_clock(clockmask);
 
-	/* Ack the  interrupt from the just-gone-off tick */
+	/* Ack the interrupt from the just-gone-off tick */
 	junk = clk[MC_REGC].datum;
 
 	return (iters);
diff --git a/sys/arch/mips/mips/mips_mcclock.h b/sys/arch/mips/mips/mips_mcclock.h
index 19d6950a079a..a4117ed7ed96 100644
--- a/sys/arch/mips/mips/mips_mcclock.h
+++ b/sys/arch/mips/mips/mips_mcclock.h
@@ -1,4 +1,4 @@
-/* $NetBSD: mips_mcclock.h,v 1.3 2002/03/05 14:12:30 simonb Exp $ */
+/* $NetBSD: mips_mcclock.h,v 1.4 2005/01/01 09:48:39 simonb Exp $ */
 
 /*
  * Copyright (c) 1997 Jonathan Stone (hereinafter referred to as the author)
@@ -40,10 +40,11 @@
  * counting iterations of an loop between successive ticks.
  */
 unsigned mc_cpuspeed(vaddr_t, int);
+int mips_mcclock_loop_with_clock(int);
+int mips_mcclock_loop_without_clock(int);
 
 /*
  * CPU speed in MHz, as estimated by mc_cpuspeed(). Read-only.
  */
 extern int cpu_mhz;
-
 #endif
diff --git a/sys/arch/mips/mips/mips_mcclock_loop.S b/sys/arch/mips/mips/mips_mcclock_loop.S
new file mode 100644
index 000000000000..5b483a6ce7a2
--- /dev/null
+++ b/sys/arch/mips/mips/mips_mcclock_loop.S
@@ -0,0 +1,102 @@
+/* $NetBSD: mips_mcclock_loop.S,v 1.1 2005/01/01 09:48:39 simonb Exp $ */
+
+/*
+ * Copyright (c) 2005 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by Simon Burge.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *        This product includes software developed by the NetBSD
+ *        Foundation, Inc. and its contributors.
+ * 4. Neither the name of The NetBSD Foundation nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <mips/asm.h>
+#include <mips/cpuregs.h>
+
+	.set	noreorder
+
+/*
+ * Provide assembly versions of the clock timing calculation loops that
+ * aren't effected by changes in compiler optimisation.
+ *
+ * These two functions are not profiled!
+ */
+
+
+LEAF_NOPROFILE(mips_mcclock_loop_with_clock)
+	subu	sp, CALLFRAME_SIZ
+	sw	s0, 0(sp)
+	sw	ra, CALLFRAME_RA(sp)
+	j	2f
+	 move	s0, zero		# iters = 0;
+1:
+	.set	push
+	.set	mips32
+	ssnop				# asm ("ssnop;ssnop;ssnop;ssnop");
+	ssnop
+	ssnop
+	ssnop
+	.set	pop
+
+	addu	s0, 1			# iters++;
+2:	jal	mips_cp0_cause_read	# v0 = mips_cp0_cause_read();
+	 nop
+	and	v0, a0			# v0 &= clockmask;
+	beqz	v0, 1b			# if zero then repeat
+	 move	v0, s0			# return iters
+	lw	ra, CALLFRAME_RA(sp)
+	lw	s0, 0(sp)
+	j	ra
+	 addu	sp, CALLFRAME_SIZ
+END(mips_mcclock_loop_with_clock)
+
+LEAF_NOPROFILE(mips_mcclock_loop_without_clock)
+	subu	sp, CALLFRAME_SIZ
+	sw	s0, 0(sp)
+	sw	ra, CALLFRAME_RA(sp)
+	j	2f
+	 move	s0, zero		# iters = 0;
+1:
+	.set	push
+	.set	mips32
+	ssnop				# asm ("ssnop;ssnop");
+	ssnop
+	.set	pop
+
+	addu	s0, 1			# iters++;
+2:	jal	mips_cp0_cause_read	# v0 = mips_cp0_cause_read();
+	 nop
+	and	v0, a0			# v0 &= clockmask;
+	beqz	v0, 1b			# if zero then repeat
+	 move	v0, s0			# return iters
+	lw	ra, CALLFRAME_RA(sp)
+	lw	s0, 0(sp)
+	j	ra
+	 addu	sp, CALLFRAME_SIZ
+END(mips_mcclock_loop_without_clock)
diff --git a/sys/arch/pmax/conf/files.pmax b/sys/arch/pmax/conf/files.pmax
index 7cc2daadde27..51e8e1b6562d 100644
--- a/sys/arch/pmax/conf/files.pmax
+++ b/sys/arch/pmax/conf/files.pmax
@@ -1,4 +1,4 @@
-#	$NetBSD: files.pmax,v 1.107 2003/12/13 23:04:37 ad Exp $
+#	$NetBSD: files.pmax,v 1.108 2005/01/01 09:48:39 simonb Exp $
 # DECstation-specific configuration info
 
 # maxpartitions must be first item in files.${ARCH}.
@@ -81,11 +81,12 @@ device	mcclock
 attach	mcclock at ioasic with mcclock_ioasic
 attach	mcclock at ibus with mcclock_ibus
 file	arch/pmax/pmax/clock.c
-file	dev/dec/mcclock.c		mcclock
-file	dev/dec/mcclock_pad32.c		mcclock
-file	arch/pmax/tc/mcclock_ioasic.c	mcclock_ioasic
-file	arch/pmax/ibus/mcclock_ibus.c	mcclock_ibus
-file	arch/mips/mips/mips_mcclock.c	mcclock # CPU speed via mcclock
+file	dev/dec/mcclock.c			mcclock
+file	dev/dec/mcclock_pad32.c			mcclock
+file	arch/pmax/tc/mcclock_ioasic.c		mcclock_ioasic
+file	arch/pmax/ibus/mcclock_ibus.c		mcclock_ibus
+file	arch/mips/mips/mips_mcclock.c		mcclock # CPU speed via mcclock
+file	arch/mips/mips/mips_mcclock_loop.S	mcclock # CPU speed via mcclock
 
 include "dev/scsipi/files.scsipi"