diff --git a/ramsurflib.c b/ramsurflib.c
index e03df71..5406c04 100644
--- a/ramsurflib.c
+++ b/ramsurflib.c
@@ -370,7 +370,7 @@ void deriv(int n, float sig, double alp,
     dh1[0][1]=sig*0.5;
     double exp1 = -0.5;
     dh2[0][0]=alp;
-    dh2[0][1]=alp;
+    dh2[0][1]=0.;
     double exp2=-1.0;
     dh3[0][0]=-2.0*nu;
     dh3[0][1]=0.;
@@ -830,7 +830,7 @@ void matrc(size_t mz, size_t mp, int const nz, int const np, int const iz, float
 static
 void updat( ramsurf_t const* rsurf, size_t *profl_index, size_t mr, size_t mz, size_t mp, int nz, int np, int *iz, int *ib,
         float dr, float dz, float omega, float k0, 
-        float r, float *rp, float rs,
+        float r, float *rp, float *rs,
         float rb[mr], float zb[mr] , float cw[mz], float cb[mz], float rhob[mz],
         float attn[mz], float alpw[mz], float alpb[mz],
         fcomplex ksq[mz], fcomplex ksqw[mz], fcomplex ksqb[mz],
@@ -871,8 +871,9 @@ void updat( ramsurf_t const* rsurf, size_t *profl_index, size_t mr, size_t mz, s
     //
     //     Turn off the stability constraints.
     //
-    if(r>=rs) {
+    if(r>=*rs) {
         int ns=0;
+        *rs=2.f*(rsurf->rmax);
         epade(mp, np, ns, 1, k0, dr, (float (*)[2])pd1, (float (*)[2])pd2);
         matrc(mz, mp, nz, np, *iz, dz, k0, rhob, alpw, alpb, (float (*)[2])ksq, (float (*)[2])ksqw, (float (*)[2])ksqb, 
                 f1, f2, f3, r1, r2, r3, s1, s2, s3, (float (*)[2])pd1, (float (*)[2])pd2, *izsrf);
@@ -1118,6 +1119,13 @@ int ramsurf(ramsurf_t const* rsurf, int * lz, float *** ogrid, FILE *fdline)
     fix_zmax(&lzmax, rsurf->rhob);
     fix_zmax(&lzmax, rsurf->attn);
 
+#ifdef __SSE3__
+    // this sets the "flush to zero" and "denormals are zero" bits (15,6) in the MXCSR register.
+    // otherwise we get very bad timings...
+    int flush_mode = _MM_GET_FLUSH_ZERO_MODE( );
+    _MM_SET_FLUSH_ZERO_MODE(_MM_FLUSH_ZERO_ON);
+#endif
+
     size_t mr = rsurf->mr,
            mz = lzmax / rsurf->dz + 2.5f,
            mp = rsurf->np;
@@ -1177,7 +1185,7 @@ int ramsurf(ramsurf_t const* rsurf, int * lz, float *** ogrid, FILE *fdline)
         //
         while (r < rsurf->rmax) {
             updat(rsurf, &profl_index, mr, mz, mp, nz, np, &iz, &ib, dr, dz, omega, k0, r, 
-                    &rp, rs, *rb, *zb, *cw, *cb, *rhob, *attn, *alpw, *alpb, *ksq, *ksqw, *ksqb, *f1, *f2, *f3, 
+                    &rp, &rs, *rb, *zb, *cw, *cb, *rhob, *attn, *alpw, *alpb, *ksq, *ksqw, *ksqb, *f1, *f2, *f3, 
                     *r1, *r2, *r3, *s1, *s2, *s3, *pd1, *pd2, *rsrf, *zsrf, &izsrf, &isrf);
             solve(mz, mp, nz, np, *u, *r1, *r3, *s1, *s2, *s3);
             r=r+dr;
@@ -1191,6 +1199,9 @@ int ramsurf(ramsurf_t const* rsurf, int * lz, float *** ogrid, FILE *fdline)
 
     // deallocation step 
     free(oscratch);
+#ifdef __SSE3__
+    _MM_SET_FLUSH_ZERO_MODE(flush_mode);
+#endif
 
     return errorCode;
 }
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 6ccb019..93dbdb2 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -1,6 +1,7 @@
-check_PROGRAMS=ramcmp
+check_PROGRAMS=ramcmp ramdump
 
 ramcmp_SOURCES=ramcmp.f
+ramdump_SOURCES=ramdump.f
 
 TESTS=decreasing_slop.sh\
 		  flat.sh\
@@ -9,7 +10,8 @@ TESTS=decreasing_slop.sh\
 		  flat_pade.sh\
 		  flat_limit.sh\
 		  increasing_slop.sh\
-		  flat_2ssps.sh
+		  flat_2ssps.sh\
+		  intensive.sh
 
 EXTRA_DIST=decreasing_slop.test\
 		  flat.test\
@@ -18,18 +20,20 @@ EXTRA_DIST=decreasing_slop.test\
 		  flat_pade.test\
 		  flat_limit.test\
 		  increasing_slop.test\
-		  flat_2ssps.test
+		  flat_2ssps.test\
+		  intensive.test
 
 SUFFIXES=.test .sh
 
 .test.sh:$(srcdir)/Makefile.am
 	echo '#!/bin/sh' > $@
 	echo 'set -e' 	>> $@
-	echo 'chmod -R u+rwx `basename $<`.d || true' >> $@
-	echo 'rm -rf `basename $<`.d' >> $@
-	echo 'cp -r $(srcdir)/`basename $<` `basename $<`.d' >> $@
-	echo 'chmod -R u+rwx `basename $<`.d' >> $@
-	echo 'cd `basename $<`.d' >> $@
+	echo 'TARGET="`basename $<`"' >> $@
+	echo 'test ! -d $$TARGET.d || chmod -R u+rwx $$TARGET.d' >> $@
+	echo 'rm -rf $$TARGET' >> $@
+	echo 'cp -r $(srcdir)/$$TARGET $$TARGET.d' >> $@
+	echo 'chmod -R u+rwx $$TARGET.d' >> $@
+	echo 'cd $$TARGET.d' >> $@
 	echo '$(abs_top_builddir)/ramsurf1.5' >> $@
 	echo 'mv tl.grid ref.grid' >> $@
 	echo 'mv tl.line ref.line' >> $@
diff --git a/tests/intensive.test/ram.in b/tests/intensive.test/ram.in
new file mode 100644
index 0000000..1368e48
--- /dev/null
+++ b/tests/intensive.test/ram.in
@@ -0,0 +1,24 @@
+header line
+2048.00	5 1000	1.0	frequency (Hz), source depth (m), tl.line depth (m)
+400000.	10	40	domain range (m), computation step (m), mesure step (comp.step)
+1000	0.2 10	1000	domain depth (m), computation step (m), mesure step (comp.step), last mesure depth (m)
+1500.000000	4	1	0.000000	reference celerity, #PADE, #stability constraints, radius of constraint
+0.0	0.0	surface depth (range, depth) (m)
+-1	-1
+   0.0000   1000.		bathymetry
+400000.000   900
+-1	-1
+   0.0000	1500
+  333.000	1500
+  334.000	1510
+  666.000	1510
+  667.000	1500
+ 1000.000	1500
+-1	-1
+0.0000000	3000.0000000
+-1	-1
+0.0000000	2.
+-1	-1
+0.0000000	0.900
+21	100.00
+-1	-1
diff --git a/tests/ramcmp.f b/tests/ramcmp.f
index 8277f26..06dd1c6 100644
--- a/tests/ramcmp.f
+++ b/tests/ramcmp.f
@@ -1,7 +1,7 @@
       program ramdec
       real tl(1000,1000)
       real rtl(1000,1000)
-      threshold = 6.8
+      threshold = .5
       open(unit=2,status='unknown',file='ref.grid', form='unformatted')
       open(unit=3,status='unknown',file='tl.grid', form='unformatted')
       read(2)nry
diff --git a/tests/ramdump.f b/tests/ramdump.f
new file mode 100644
index 0000000..48f9e4f
--- /dev/null
+++ b/tests/ramdump.f
@@ -0,0 +1,15 @@
+      program ramdec
+      real tl(1000,1000)
+      CHARACTER(len=256) :: arg
+      threshold = .3
+      eps = 1e-10
+      CALL get_command_argument(1, arg)
+      open(unit=2,status='unknown',file=arg, form='unformatted')
+      read(2)nry
+      nx=1
+    5 read(2,end=6)(tl(j,nx),j=1,nry)
+      write(*,*)(tl(j,nx) ,j=1,nry)
+      nx=nx+1
+      go to 5
+    6 end
+