diff --git a/benchmarks.larceny/results.Larceny-r6rs b/benchmarks.larceny/results.Larceny-r6rs
index bfccfe4..a32f619 100644
--- a/benchmarks.larceny/results.Larceny-r6rs
+++ b/benchmarks.larceny/results.Larceny-r6rs
@@ -8514,3 +8514,23 @@ Words allocated: 29621942
 Words reclaimed: 0
 Elapsed time...: 1199 ms (User: 1195 ms; System: 4 ms)
 Elapsed GC time: 44 ms (CPU: 48 in 113 collections.)
+
+****************************
+Benchmarking Larceny-r6rs on Thu Nov 8 20:58:17 EST 2007 under Darwin Vesuvius.local 8.10.1 Darwin Kernel Version 8.10.1: Wed May 23 16:33:00 PDT 2007; root:xnu-792.22.5~1/RELEASE_I386 i386 i386
+
+Testing maze under Larceny-r6rs
+Compiling...
+Larceny v0.93 "Deviated Prevert" (Nov 10 2006 04:27:45, precise:BSD Unix:unified)
+
+
+> 
+> 
+Running...
+Larceny v0.93 "Deviated Prevert" (Nov 10 2006 04:27:45, precise:BSD Unix:unified)
+
+
+> 
+Words allocated: 36171538
+Words reclaimed: 0
+Elapsed time...: 5849 ms (User: 5815 ms; System: 31 ms)
+Elapsed GC time: 83 ms (CPU: 86 in 138 collections.)
diff --git a/scheme/ikarus.boot.orig b/scheme/ikarus.boot.orig
index 33af517..63fff55 100644
Binary files a/scheme/ikarus.boot.orig and b/scheme/ikarus.boot.orig differ
diff --git a/scheme/ikarus.bytevectors.ss b/scheme/ikarus.bytevectors.ss
index 7cb5d1b..52763a9 100644
--- a/scheme/ikarus.bytevectors.ss
+++ b/scheme/ikarus.bytevectors.ss
@@ -33,7 +33,9 @@
     bytevector->uint-list bytevector->sint-list
     uint-list->bytevector sint-list->bytevector
     bytevector-ieee-double-native-ref bytevector-ieee-double-native-set!
+    bytevector-ieee-single-native-ref bytevector-ieee-single-native-set!
     bytevector-ieee-double-ref bytevector-ieee-double-set!
+    bytevector-ieee-single-ref bytevector-ieee-single-set!
     native-endianness)
   (import 
     (except (ikarus) 
@@ -55,8 +57,9 @@
       uint-list->bytevector sint-list->bytevector
       bytevector-ieee-double-native-ref bytevector-ieee-double-native-set!
       bytevector-ieee-double-ref bytevector-ieee-double-set!
+      bytevector-ieee-single-native-ref bytevector-ieee-single-native-set!
+      bytevector-ieee-single-ref bytevector-ieee-single-set!
       native-endianness)
-    ;(only (rnrs) bitwise-and)
     (ikarus system $fx)
     (ikarus system $bignums)
     (ikarus system $pairs)
@@ -972,30 +975,52 @@
     (if (bytevector? bv) 
         (if (and (fixnum? i) 
                  ($fx>= i 0)
-                 ($fxzero? ($fxlogand i 3))
+                 ($fxzero? ($fxlogand i 7))
                  ($fx< i ($bytevector-length bv)))
             ($bytevector-ieee-double-native-ref bv i)
             (error 'bytevector-ieee-double-native-ref "invalid index" i))
         (error 'bytevector-ieee-double-native-ref "not a bytevector" bv)))
 
-  (define (bytevector-ieee-double-native-set! bv i x) 
+  (define (bytevector-ieee-single-native-ref bv i)
     (if (bytevector? bv) 
         (if (and (fixnum? i) 
                  ($fx>= i 0)
                  ($fxzero? ($fxlogand i 3))
                  ($fx< i ($bytevector-length bv)))
+            ($bytevector-ieee-single-native-ref bv i)
+            (error 'bytevector-ieee-single-native-ref "invalid index" i))
+        (error 'bytevector-ieee-single-native-ref "not a bytevector" bv)))
+
+  (define (bytevector-ieee-double-native-set! bv i x) 
+    (if (bytevector? bv) 
+        (if (and (fixnum? i) 
+                 ($fx>= i 0)
+                 ($fxzero? ($fxlogand i 7))
+                 ($fx< i ($bytevector-length bv)))
             (if (flonum? x) 
                 ($bytevector-ieee-double-native-set! bv i x)
                 (error 'bytevector-ieee-double-native-set! "not a flonum" x))
             (error 'bytevector-ieee-double-native-set! "invalid index" i))
         (error 'bytevector-ieee-double-native-set! "not a bytevector" bv)))
    
-  (define (bytevector-ieee-double-ref bv i endianness) 
+  (define (bytevector-ieee-single-native-set! bv i x) 
     (if (bytevector? bv) 
         (if (and (fixnum? i) 
                  ($fx>= i 0)
                  ($fxzero? ($fxlogand i 3))
                  ($fx< i ($bytevector-length bv)))
+            (if (flonum? x) 
+                ($bytevector-ieee-single-native-set! bv i x)
+                (error 'bytevector-ieee-single-native-set! "not a flonum" x))
+            (error 'bytevector-ieee-single-native-set! "invalid index" i))
+        (error 'bytevector-ieee-single-native-set! "not a bytevector" bv)))
+
+  (define (bytevector-ieee-double-ref bv i endianness) 
+    (if (bytevector? bv) 
+        (if (and (fixnum? i) 
+                 ($fx>= i 0)
+                 ($fxzero? ($fxlogand i 7))
+                 ($fx< i ($bytevector-length bv)))
             (case endianness
               [(little) ($bytevector-ieee-double-native-ref bv i)]
               [(big) ($bytevector-ieee-double-nonnative-ref bv i)]
@@ -1004,12 +1029,26 @@
             (error 'bytevector-ieee-double-ref "invalid index" i))
         (error 'bytevector-ieee-double-ref "not a bytevector" bv)))
 
-  (define (bytevector-ieee-double-set! bv i x endianness) 
+  (define (bytevector-ieee-single-ref bv i endianness) 
     (if (bytevector? bv) 
         (if (and (fixnum? i) 
                  ($fx>= i 0)
                  ($fxzero? ($fxlogand i 3))
                  ($fx< i ($bytevector-length bv)))
+            (case endianness
+              [(little) ($bytevector-ieee-single-native-ref bv i)]
+              ;[(big) ($bytevector-ieee-single-nonnative-ref bv i)]
+              [else (error 'bytevector-ieee-single-ref 
+                      "invalid endianness" endianness)])
+            (error 'bytevector-ieee-single-ref "invalid index" i))
+        (error 'bytevector-ieee-single-ref "not a bytevector" bv)))
+
+  (define (bytevector-ieee-double-set! bv i x endianness) 
+    (if (bytevector? bv) 
+        (if (and (fixnum? i) 
+                 ($fx>= i 0)
+                 ($fxzero? ($fxlogand i 7))
+                 ($fx< i ($bytevector-length bv)))
             (if (flonum? x)
                 (case endianness
                   [(little) ($bytevector-ieee-double-native-set! bv i x)]
@@ -1020,6 +1059,22 @@
             (error 'bytevector-ieee-double-set! "invalid index" i))
         (error 'bytevector-ieee-double-set! "not a bytevector" bv)))
 
+  (define (bytevector-ieee-single-set! bv i x endianness) 
+    (if (bytevector? bv) 
+        (if (and (fixnum? i) 
+                 ($fx>= i 0)
+                 ($fxzero? ($fxlogand i 3))
+                 ($fx< i ($bytevector-length bv)))
+            (if (flonum? x)
+                (case endianness
+                  [(little) ($bytevector-ieee-single-native-set! bv i x)]
+              ;    [(big) ($bytevector-ieee-single-nonnative-set! bv i x)]
+                  [else (error 'bytevector-ieee-single-set! 
+                          "invalid endianness" endianness)])
+                (error 'bytevector-ieee-single-set! "not a flonum" x))
+            (error 'bytevector-ieee-single-set! "invalid index" i))
+        (error 'bytevector-ieee-single-set! "not a bytevector" bv)))
+
   )
 
 
diff --git a/scheme/ikarus.compiler.altcogen.ss b/scheme/ikarus.compiler.altcogen.ss
index b217445..c7ce503 100644
--- a/scheme/ikarus.compiler.altcogen.ss
+++ b/scheme/ikarus.compiler.altcogen.ss
@@ -548,11 +548,13 @@
                   (make-disp (car s*) (cadr s*)) 
                   (caddr s*))))]
          [(fl:load fl:store fl:add! fl:sub! fl:mul! fl:div!
-                   fl:from-int fl:shuffle bswap!) 
+                   fl:from-int fl:shuffle bswap!
+                   fl:store-single fl:load-single) 
           (S* rands
               (lambda (s*)
                 (make-asm-instr op (car s*) (cadr s*))))]
-         [(nop interrupt incr/zero?) x]
+         [(nop interrupt incr/zero? fl:double->single
+               fl:single->double) x]
          [else (error 'impose-effect "invalid instr" x)])]
       [(funcall rator rands)
        (handle-nontail-call rator rands #f #f)]
@@ -1504,7 +1506,8 @@
           (mark-reg/vars-conf! edx vs)
           (R s vs (rem-reg edx rs) fs ns)]
          [(mset bset/c bset/h fl:load fl:store fl:add! fl:sub!
-                fl:mul! fl:div! fl:from-int fl:shuffle) 
+                fl:mul! fl:div! fl:from-int fl:shuffle
+                fl:load-single fl:store-single) 
           (R* (list s d) vs rs fs ns)]
          [else (error who "invalid effect op" (unparse x))])]
       [(ntcall target value args mask size)
@@ -1517,7 +1520,7 @@
        (E body vs rs fs ns)]
       [(primcall op args)
        (case op
-         [(nop) (values vs rs fs ns)]
+         [(nop fl:double->single fl:single->double) (values vs rs fs ns)]
          [(interrupt incr/zero?) 
           (let ([v (exception-live-set)])
             (unless (vector? v)
@@ -1709,7 +1712,7 @@
               sll sra srl bswap!
               cltd idiv int-/overflow int+/overflow int*/overflow
               fl:load fl:store fl:add! fl:sub! fl:mul! fl:div!
-              fl:from-int fl:shuffle)
+              fl:from-int fl:shuffle fl:load-single fl:store-single)
             (make-asm-instr op (R d) (R s))]
            [(nop) (make-primcall 'nop '())]
            [else (error who "invalid op" op)])]
@@ -1809,7 +1812,8 @@
              (NFE (fxsub1 i) (make-mask (fxsub1 i)) body)))]
         [(primcall op args)
          (case op
-           [(nop interrupt incr/zero?) x]
+           [(nop interrupt incr/zero? fl:double->single
+                 fl:single->double) x]
            [else (error who "invalid effect prim" op)])]
         [(shortcut body handler)
          (make-shortcut (E body) (E handler))]
@@ -1956,7 +1960,8 @@
               (set-union (set-union (R eax) (R edx))
                      (set-union (R v) s)))]
            [(mset fl:load fl:store fl:add! fl:sub! fl:mul! fl:div!
-                  fl:from-int fl:shuffle)
+                  fl:from-int fl:shuffle fl:store-single
+                  fl:load-single)
             (set-union (R v) (set-union (R d) s))]
            [else (error who "invalid effect" x)])]
         [(seq e0 e1) (E e0 (E e1 s))]
@@ -1967,7 +1972,7 @@
          (set-union (R* args) s)]
         [(primcall op arg*)
          (case op
-           [(nop) s]
+           [(nop fl:single->double fl:double->single) s]
            [(interrupt incr/zero?) 
             (or (exception-live-set) (error who "uninitialized exception"))]
            [else (error who "invalid effect primcall" op)])]
@@ -2289,7 +2294,8 @@
                         (E (make-asm-instr 'move u s2))
                         (E (make-asm-instr op (make-disp u s1) b))))]
                    [else x]))])]
-           [(fl:load fl:store fl:add! fl:sub! fl:mul! fl:div!) 
+           [(fl:load fl:store fl:add! fl:sub! fl:mul! fl:div!
+             fl:load-single fl:store-single) 
             (cond
               [(mem? a) 
                (let ([u (mku)])
@@ -2301,7 +2307,8 @@
            [else (error who "invalid effect" op)])]
         [(primcall op rands) 
          (case op
-           [(nop interrupt incr/zero?) x]
+           [(nop interrupt incr/zero? fl:single->double
+                 fl:double->single) x]
            [else (error who "invalid op in" (unparse x))])]
         [(ntcall) x]
         [(shortcut body handler)
@@ -2581,8 +2588,12 @@
                    ac))]
          [(fl:store) 
           (cons `(movsd xmm0 ,(R (make-disp s d))) ac)]
+         [(fl:store-single) 
+          (cons `(movss xmm0 ,(R (make-disp s d))) ac)]
          [(fl:load) 
           (cons `(movsd ,(R (make-disp s d)) xmm0) ac)]
+         [(fl:load-single) 
+          (cons `(movss ,(R (make-disp s d)) xmm0) ac)]
          [(fl:from-int) 
           (cons `(cvtsi2sd ,(R s) xmm0) ac)]
          [(fl:shuffle) 
@@ -2610,6 +2621,10 @@
               `(addl 1 ,(R (make-disp (car rands) (cadr rands))))
               `(je ,l)
               ac))]
+         [(fl:double->single)
+          (cons '(cvtsd2ss xmm0 xmm0) ac)]
+         [(fl:single->double)
+          (cons '(cvtss2sd xmm0 xmm0) ac)]
          [else (error who "invalid effect" (unparse x))])]
       [(shortcut body handler)
        (let ([L (unique-interrupt-label)] [L2 (unique-label)])
diff --git a/scheme/ikarus.intel-assembler.ss b/scheme/ikarus.intel-assembler.ss
index 9d7a508..5b1cec7 100644
--- a/scheme/ikarus.intel-assembler.ss
+++ b/scheme/ikarus.intel-assembler.ss
@@ -504,6 +504,27 @@
       [(and (xmmreg? dst) (mem? src))
        (CODE #xF2 (CODE #x0F ((CODE/digit #x2A dst) src ac)))]
       [else (error who "invalid" instr)])] 
+   [(cvtsd2ss src dst)
+    (cond
+      [(and (xmmreg? dst) (reg? src))
+       (CODE #xF2 (CODE #x0F (CODE #x5A (ModRM 3 src dst ac))))]
+      ;[(and (xmmreg? dst) (mem? src))
+      ; (CODE #xF2 (CODE #x0F ((CODE/digit #x5A dst) src ac)))]
+      [else (error who "invalid" instr)])]
+   [(cvtss2sd src dst)
+    (cond
+      [(and (xmmreg? dst) (reg? src))
+       (CODE #xF3 (CODE #x0F (CODE #x5A (ModRM 3 src dst ac))))]
+      ;[(and (xmmreg? dst) (mem? src))
+      ; (CODE #xF3 (CODE #x0F ((CODE/digit #x5A dst) src ac)))]
+      [else (error who "invalid" instr)])]
+   [(movss src dst)
+    (cond
+      [(and (xmmreg? dst) (or (xmmreg? src) (mem? src)))
+       (CODE #xF3 (CODE #x0F ((CODE/digit #x10 dst) src ac)))]
+      [(and (xmmreg? src) (or (xmmreg? dst) (mem? dst)))
+       (CODE #xF3 (CODE #x0F ((CODE/digit #x11 src) dst ac)))]
+      [else (error who "invalid" instr)])]
    [(addsd src dst)
     (cond
       [(and (xmmreg? dst) (or (xmmreg? src) (mem? src)))
diff --git a/scheme/makefile.ss b/scheme/makefile.ss
index e2aae51..48ba6e1 100755
--- a/scheme/makefile.ss
+++ b/scheme/makefile.ss
@@ -411,6 +411,10 @@
     [$bytevector-ieee-double-native-set!         $bytes]
     [$bytevector-ieee-double-nonnative-ref       $bytes]
     [$bytevector-ieee-double-nonnative-set!      $bytes]
+    [$bytevector-ieee-single-native-ref          $bytes]
+    [$bytevector-ieee-single-native-set!         $bytes]
+    [$bytevector-ieee-single-nonnative-ref       $bytes]
+    [$bytevector-ieee-single-nonnative-set!      $bytes]
     [$flonum-u8-ref                              $flonums]
     [$make-flonum                                $flonums]
     [$flonum-set!                                $flonums]
@@ -867,9 +871,10 @@
     [bytevector-ieee-double-native-set!          i r bv]
     [bytevector-ieee-double-ref                  i r bv]
     [bytevector-ieee-double-set!                 i r bv]
-    [bytevector-ieee-single-native-ref           r bv]
-    [bytevector-ieee-single-native-set!          r bv]
-    [bytevector-ieee-single-ref                  r bv]
+    [bytevector-ieee-single-native-ref           i r bv]
+    [bytevector-ieee-single-native-set!          i r bv]
+    [bytevector-ieee-single-ref                  i r bv]
+    [bytevector-ieee-single-set!                  i r bv]
     [bytevector-length                           i r bv]
     [bytevector-s16-native-ref                   i r bv]
     [bytevector-s16-native-set!                  i r bv]
diff --git a/scheme/pass-specify-rep-primops.ss b/scheme/pass-specify-rep-primops.ss
index 644e797..6cb7a33 100644
--- a/scheme/pass-specify-rep-primops.ss
+++ b/scheme/pass-specify-rep-primops.ss
@@ -1438,6 +1438,7 @@
      (prm 'fl:store x (K (- disp-flonum-data vector-tag)))
      x)])
 
+
 ;;; the following uses unsupported sse3 instructions
 ;(define-primop $bytevector-ieee-double-nonnative-ref unsafe
 ;  [(V bv i)
@@ -1477,6 +1478,27 @@
        (prm 'int+ (T bv) (prm 'sra (T i) (K fixnum-shift)))
        (K (- disp-bytevector-data bytevector-tag))))])
 
+
+(define-primop $bytevector-ieee-single-native-ref unsafe
+  [(V bv i)
+   (with-tmp ([x (prm 'alloc (K (align flonum-size)) (K vector-tag))])
+     (prm 'mset x (K (- vector-tag)) (K flonum-tag))
+     (prm 'fl:load-single
+       (prm 'int+ (T bv) (prm 'sra (T i) (K fixnum-shift)))
+       (K (- disp-bytevector-data bytevector-tag)))
+     (prm 'fl:single->double)
+     (prm 'fl:store x (K (- disp-flonum-data vector-tag)))
+     x)])
+
+(define-primop $bytevector-ieee-single-native-set! unsafe
+  [(E bv i x)
+   (seq*
+     (prm 'fl:load (T x) (K (- disp-flonum-data vector-tag)))
+     (prm 'fl:double->single)
+     (prm 'fl:store-single
+       (prm 'int+ (T bv) (prm 'sra (T i) (K fixnum-shift)))
+       (K (- disp-bytevector-data bytevector-tag))))])
+
 ;;; the following uses unsupported sse3 instructions
 ;(define-primop $bytevector-ieee-double-nonnative-set! unsafe
 ;  [(E bv i x)
diff --git a/scheme/tests/bytevectors.ss b/scheme/tests/bytevectors.ss
index e94b189..4408b53 100644
--- a/scheme/tests/bytevectors.ss
+++ b/scheme/tests/bytevectors.ss
@@ -272,6 +272,7 @@
      (let ([v (make-bytevector 4)])
        (bytevector-s32-set! v 0 -12345 'little)
        (bytevector-s32-ref v 0 'little))]
+
     [(lambda (x) (= x -12345))
      (let ([v (make-bytevector 4)])
        (bytevector-s32-set! v 0 -12345 'big)
@@ -306,6 +307,38 @@
                    (reverse (bytevector->u8-list v1)))])
          (bytevector-ieee-double-ref v2 0 'little)))]
 
+    [(lambda (x) (= x 17.0))
+     (let ([v (make-bytevector 4)])
+       (bytevector-ieee-single-native-set! v 0 17.0)
+       (bytevector-ieee-single-native-ref v 0))]
+
+    [(lambda (x) (= x 17.0))
+     (let ([v (make-bytevector 4)])
+       (bytevector-ieee-single-set! v 0 17.0 'little)
+       (bytevector-ieee-single-ref v 0 'little))]
+
+;    [(lambda (x) (= x 17.0))
+;     (let ([v (make-bytevector 8)])
+;       (bytevector-ieee-single-set! v 0 17.0 'big)
+;       (bytevector-ieee-single-ref v 0 'big))]
+;    
+;    [(lambda (x) (= x 17.0))
+;     (let ([v1 (make-bytevector 8)])
+;       (bytevector-ieee-single-set! v1 0 17.0 'little)
+;       (let ([v2 (u8-list->bytevector
+;                   (reverse (bytevector->u8-list v1)))])
+;         (bytevector-ieee-single-ref v2 0 'big)))]
+;
+;    [(lambda (x) (= x 17.0))
+;     (let ([v1 (make-bytevector 8)])
+;       (bytevector-ieee-single-set! v1 0 17.0 'big)
+;       (let ([v2 (u8-list->bytevector
+;                   (reverse (bytevector->u8-list v1)))])
+;         (bytevector-ieee-single-ref v2 0 'little)))]
+
+
+
+
     ))
 
 
diff --git a/scheme/todo-r6rs.ss b/scheme/todo-r6rs.ss
index db43bbd..268dbf2 100755
--- a/scheme/todo-r6rs.ss
+++ b/scheme/todo-r6rs.ss
@@ -255,7 +255,7 @@
     [bitwise-arithmetic-shift                   C bw]
     [bitwise-arithmetic-shift-left              C bw]
     [bitwise-arithmetic-shift-right             C bw]
-    [bitwise-not                                S bw]
+    [bitwise-not                                C bw]
     [bitwise-and                                C bw]
     [bitwise-ior                                S bw]
     [bitwise-xor                                S bw]