diff --git ./sysdeps/alpha/alphaev6/memcpy.S ./sysdeps/alpha/alphaev6/memcpy.S
index 7f5799ecac..cf5c97c1de 100644
--- ./sysdeps/alpha/alphaev6/memcpy.S
+++ ./sysdeps/alpha/alphaev6/memcpy.S
@@ -87,9 +87,16 @@ $single_head_quad:
 $do_unroll:
 	/*
 	 * Dispatch on the CPU implementation.  The 21264 (EV6, EV67, EV68)
-	 * issues wh64 one trip ahead of the stores to avoid read-for-ownership
-	 * on whole-line stores into the destination.  That distance is far too
-	 * short for the 21364 (EV7), whose on-chip memory controller has a much
+	 * issues wh64 two lines ahead of the stores to avoid read-for-ownership
+	 * on whole-line stores into the destination.  wh64 has to claim the line
+	 * before the stores reach it and, unlike a load prefetch, there is no
+	 * fill latency for a late hint to hide behind, so a one-line lead is too
+	 * short to do much good.  Going deeper than two costs more than it
+	 * returns here: the loads of this loop already supply some slack, so the
+	 * gain past two lines is under 1%, while the stretch at the end of the
+	 * region that has to fall back to hinting the current block grows and
+	 * makes short copies slower.  memset, which has no load stream to hide
+	 * behind, needs four.  wh64 is far too
 	 * longer latency: there wh64 neither overlaps the fill nor avoids the
 	 * Mbox replay traps it provokes in the store stream.  EV7 takes its own
 	 * unrolled loop that software-prefetches both streams several lines
@@ -106,9 +113,17 @@ $do_unroll:
 	subq	$2, 3, $2		# E : EV7 -> 0
 
 	beq	$2, $ev7_unroll		# U : EV7 takes the prefetch-modify path
-	addq	$16, 64, $7		# E : Initial (+1 trip) wh64 address
-	nop				# E :
-	nop				# E :
+
+	/*
+	 * Initial wh64 target, two lines (128 bytes) ahead of the first block.
+	 * The loop is only known to have 128 bytes left at this point, so the
+	 * first hint can overrun where the steady-state one cannot; if there is
+	 * not room for it, hint the first block instead.  wh64 makes the whole
+	 * 64-byte block UNPREDICTABLE, so an overrunning hint corrupts memory.
+	 */
+	addq	$16, 128, $7		# E : initial (+2 line) wh64 address
+	subq	$18, 192, $2		# E : room for [$16+128, $16+192)?
+	cmovlt	$2, $16, $7		# E : no -- hint the first block instead
 
 $unroll_body:
 	wh64	($7)			# L1 : memory subsystem hint: 64 bytes at
@@ -134,7 +149,11 @@ $unroll_body:
 
 	stq	$4, 8($16)		# L : bytes 8..15
 	stq	$5, 16($16)		# L : bytes 16..23
-	subq	$18, 192, $2		# E : At least two more trips to go?
+	lda	$2, -256($18)		# E : room for the +2 line hint next trip?
+					#     it covers [$16+128, $16+192) there,
+					#     so that trip needs 192 and this one
+					#     needs 256 (256 exceeds the subq
+					#     literal field, hence lda)
 	nop				# E :
 
 	stq	$3, 24($16)		# L : bytes 24..31