diff --git a/bin/ikarus b/bin/ikarus
index 6ccad4e..d4b1fd7 100755
Binary files a/bin/ikarus and b/bin/ikarus differ
diff --git a/bin/ikarus-collect.c b/bin/ikarus-collect.c
index 49ec8f5..70966ab 100644
--- a/bin/ikarus-collect.c
+++ b/bin/ikarus-collect.c
@@ -376,7 +376,6 @@ ik_collect(int mem_req, ikpcb* pcb){
     add_to_collect_count(pcb, bytes);
   }
 
-
   struct rusage t0, t1;
   struct timeval rt0, rt1;
   gettimeofday(&rt0, 0);
@@ -496,11 +495,13 @@ ik_collect(int mem_req, ikpcb* pcb){
   int free_space = 
     ((unsigned int)pcb->allocation_redline) - 
     ((unsigned int)pcb->allocation_pointer);
-  if(free_space <= mem_req){
+  #define HEAPSIZE (1024 * 4096)
+  if((free_space <= mem_req) || (pcb->heap_size < HEAPSIZE)){
 #ifndef NDEBUG
     fprintf(stderr, "REQ=%d, got %d\n", mem_req, free_space);
 #endif
-    int memsize = align_to_next_page(mem_req);
+    int memsize = (mem_req>HEAPSIZE) ? mem_req : HEAPSIZE;
+    memsize = align_to_next_page(memsize);
     ik_munmap_from_segment(
         pcb->heap_base,
         pcb->heap_size,
diff --git a/bin/ikarus-runtime.c b/bin/ikarus-runtime.c
index 2b95a38..dbc08a8 100644
--- a/bin/ikarus-runtime.c
+++ b/bin/ikarus-runtime.c
@@ -457,7 +457,6 @@ char* ik_uuid(char* str){
 static const char* uuid_chars = 
 "!$%&/0123456789<=>?ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
 static int uuid_strlen = 1;
-
 ikp ik_uuid(ikp str){
   static int fd = -1;
   if(fd == -1){
diff --git a/src/ikarus.boot b/src/ikarus.boot
index d89ba36..b0a1af2 100644
Binary files a/src/ikarus.boot and b/src/ikarus.boot differ
diff --git a/src/ikarus.fixnums.ss b/src/ikarus.fixnums.ss
index 338439d..01d3c2f 100644
--- a/src/ikarus.fixnums.ss
+++ b/src/ikarus.fixnums.ss
@@ -250,7 +250,9 @@
         (error 'fxarithmetic-shift "~s is not a fixnum" y))
       (if ($fx>= y 0)
           ($fxsll x y)
-          ($fxsra x ($fx- 0 y)))))
+          (if ($fx< x -100) ;;; arbitrary number < (fixnum-width)
+              ($fxsra x 32)
+              ($fxsra x ($fx- 0 y))))))
 
   (define (fxpositive? x)
     (if (fixnum? x) 
diff --git a/src/ikarus.singular-objects.ss b/src/ikarus.singular-objects.ss
index 861af9c..01890da 100644
--- a/src/ikarus.singular-objects.ss
+++ b/src/ikarus.singular-objects.ss
@@ -1,13 +1,15 @@
 
 (library (ikarus singular-objects)
-  (export base-rtd eof-object void)
+  (export base-rtd eof-object void #;fixnum-width)
   (import 
     (rename (ikarus system $records) (base-rtd sys:base-rtd))
     (rename (ikarus)
             (void sys:void)
+           #; (fixnum-width sys:fixnum-width)
             (eof-object sys:eof-object)))
 
   (define (void) (sys:void))
+#;  (define (fixnum-width) (sys:fixnum-width))
   (define (eof-object) (sys:eof-object))
   (define (base-rtd) (sys:base-rtd)))
 
diff --git a/src/makefile.ss b/src/makefile.ss
index 6a605cb..2cc1f32 100755
--- a/src/makefile.ss
+++ b/src/makefile.ss
@@ -459,6 +459,7 @@
     [fxarithmetic-shift       i]
     [fxmin       i]
     [fxmax       i]
+    [fixnum-width i]
 
     [for-each                i r]
     [map                     i r]
diff --git a/src/pass-specify-rep-primops.ss b/src/pass-specify-rep-primops.ss
index 2359371..85d4125 100644
--- a/src/pass-specify-rep-primops.ss
+++ b/src/pass-specify-rep-primops.ss
@@ -545,6 +545,15 @@
   [(P x) (tag-test (T x) fixnum-mask fixnum-tag)]
   [(E x) (nop)])
 
+;(define-primop foo safe
+;  [(V) (K 0)])
+
+;(define-primop fixnum-width safe
+;  [(V) (K 0)] ;(K (fxsll (- (* wordsize 8) fx-shift) fx-shift))]
+;  ;[(E) (nop)]
+;  ;[(P) (K #t)]
+;  )
+
 (define-primop $fxzero? unsafe
   [(P x) (prm '= (T x) (K 0))]
   [(E x) (nop)])
diff --git a/src/pass-specify-rep.ss b/src/pass-specify-rep.ss
index b3def2c..4507903 100644
--- a/src/pass-specify-rep.ss
+++ b/src/pass-specify-rep.ss
@@ -18,7 +18,6 @@
   (define fixnum-mask 3))
 
 (module primops (primop? get-primop set-primop!)
-
   (define cookie (gensym))
   (define (primop? x)
     (and (getprop x cookie) #t))