diff --git a/mps/src/arena.c b/mps/src/arena.c
index bcd48dc550e..3939991501d 100644
--- a/mps/src/arena.c
+++ b/mps/src/arena.c
@@ -1,6 +1,6 @@
 /* impl.c.arena: ARENA IMPLEMENTATION
  *
- * $HopeName: MMsrc!arena.c(trunk.8) $
+ * $HopeName: MMsrc!arena.c(trunk.9) $
  * Copyright (C) 1997 The Harlequin Group Limited.  All rights reserved.
  *
  * .readership: Any MPS developer
@@ -40,7 +40,7 @@
 /* finalization */
 #include "poolmrg.h"
 
-SRCID(arena, "$HopeName: MMsrc!arena.c(trunk.8) $");
+SRCID(arena, "$HopeName: MMsrc!arena.c(trunk.9) $");
 
 
 /* All static data objects are declared here. See .static */
@@ -110,6 +110,7 @@ Bool ArenaCheck(Arena arena)
 
   /* no check possible on arena->pollThreshold */
   CHECKL(BoolCheck(arena->insidePoll));
+  CHECKL(BoolCheck(arena->clamped));
 
   /* no check on arena->actionInterval */
   CHECKL(arena->allocTime >= 0.0);
@@ -232,6 +233,7 @@ void ArenaInit(Arena arena, ArenaClass class)
     arena->shCache[i] = (Seg)0;
   arena->pollThreshold = (Size)0;
   arena->insidePoll = FALSE;
+  arena->clamped = FALSE;
   /* design.mps.arena.poll.interval */
   arena->actionInterval = ARENA_POLL_MAX;  
   arena->epoch = (Epoch)0;              /* impl.c.ld */
@@ -513,6 +515,9 @@ void ArenaPoll(Arena arena)
 
   AVERT(Arena, arena);
 
+  if(arena->clamped)
+    return;
+
   size = ArenaCommitted(arena);
   if(arena->insidePoll || size < arena->pollThreshold)
     return;
diff --git a/mps/src/awlut.c b/mps/src/awlut.c
index 905c1c4c562..ea2d4381b29 100644
--- a/mps/src/awlut.c
+++ b/mps/src/awlut.c
@@ -1,6 +1,6 @@
 /* impl.c.awlut: POOL CLASS AWL UNIT TEST
  *
- * $HopeName: MMsrc!awlut.c(trunk.7) $
+ * $HopeName: MMsrc!awlut.c(trunk.8) $
  * Copyright (C) 1997 The Harlequin Group Limited.  All rights reserved.
  *
  * READERSHIP
@@ -40,8 +40,9 @@ static mps_word_t bogus_class;
 static mps_word_t wrapper_wrapper[] = {
   (mps_word_t)wrapper_wrapper,	/* wrapper */
   (mps_word_t)&bogus_class,	/* class */
-  3<<2|2,			/* F */
-  1<<(MPS_WORD_WIDTH - 8),	/* V */
+  0,                            /* Extra word */
+  4<<2|2,			/* F */
+  2<<(MPS_WORD_WIDTH - 8),	/* V */
   1<<2|1,			/* VL */
   1				/* patterns */
 };
@@ -50,16 +51,18 @@ static mps_word_t wrapper_wrapper[] = {
 static mps_word_t string_wrapper[] = {
   (mps_word_t)wrapper_wrapper,	/* wrapper */
   (mps_word_t)&bogus_class,	/* class */
+  0,                            /* extra word */
   0,				/* F */
-  1<<(MPS_WORD_WIDTH - 8)|3<<3|4,	/* V */
+  2<<(MPS_WORD_WIDTH - 8)|3<<3|4,	/* V */
   1				/* VL */
 };
 
 static mps_word_t table_wrapper[] = {
   (mps_word_t)wrapper_wrapper,  /* wrapper */
   (mps_word_t)&bogus_class,	/* class */
+  0,                            /* extra word */
   1<<2|1,			/* F */
-  1<<(MPS_WORD_WIDTH - 8)|2,	/* V */
+  2<<(MPS_WORD_WIDTH - 8)|2,	/* V */
   1				/* VL */
 };
 
@@ -104,7 +107,7 @@ static mps_word_t *alloc_table(unsigned long n, mps_ap_t ap)
   size_t objsize;
   void *p;
   mps_word_t *object;
-  objsize = (3 + n) * sizeof(mps_word_t);
+  objsize = (4 + n) * sizeof(mps_word_t);
   objsize = (objsize + MPS_PF_ALIGN-1)/MPS_PF_ALIGN*MPS_PF_ALIGN;
   do {
     unsigned long i;
diff --git a/mps/src/comm.gmk b/mps/src/comm.gmk
index 37e9cfe98b3..d7be9be894b 100644
--- a/mps/src/comm.gmk
+++ b/mps/src/comm.gmk
@@ -1,6 +1,6 @@
 # impl.gmk.comm: COMMON GNUMAKEFILE FRAGMENT
 #
-# $HopeName: MMsrc!comm.gmk(trunk.19) $
+# $HopeName: MMsrc!comm.gmk(trunk.20) $
 # Copyright (C) 1995,1996,1997 Harlequin Group, all rights reserved
 #
 # DESCRIPTION
@@ -146,6 +146,14 @@ CFCE = -DCONFIG_VAR_CE          $(CFLAGSCOOL) $(CFLAGSEXTERNAL)
 CFWI = -DCONFIG_VAR_WI -DNDEBUG $(CFLAGSHOT)  $(CFLAGSINTERNAL)
 
 
+# == Common definitions ==
+# %%PART: Add your part here, unless it's platform-specific
+# These values are defined here because they have no variation between
+# platforms.
+ 
+FMTDY = fmtdy.c fmtdytst.c
+  
+   
 # These map the source file lists onto object files and dependency files
 # in the platform/variety directory.
 # 
@@ -182,6 +190,8 @@ endif
 endif
 TESTLIBOBJ = $(TESTLIB:%.c=$(PFM)/$(VARIETY)/%.o)
 TESTLIBDEP = $(TESTLIB:%.c=$(PFM)/$(VARIETY)/%.d)
+FMTDYOBJ = $(FMTDY:%.c=$(PFM)/$(VARIETY)/%.o)
+FMTDYDEP = $(FMTDY:%.c=$(PFM)/$(VARIETY)/%.d)
 endif
 
 # Bind CFLAGS to the appropriate set of flags for the variety.
@@ -281,8 +291,7 @@ $(PFM)/$(VARIETY)/mpmconft: $(PFM)/$(VARIETY)/mpmconft.o \
 	$(MPMOBJ)
 
 $(PFM)/$(VARIETY)/finalcv: $(PFM)/$(VARIETY)/finalcv.o \
-	$(PFM)/$(VARIETY)/fmtdy.o \
-	$(MPMOBJ) $(AMCOBJ) $(TESTLIBOBJ)
+	$(FMTDYOBJ) $(MPMOBJ) $(AMCOBJ) $(TESTLIBOBJ)
 
 $(PFM)/$(VARIETY)/locv: $(PFM)/$(VARIETY)/locv.o \
 	$(MPMOBJ) $(LOOBJ) $(TESTLIBOBJ)
@@ -294,23 +303,19 @@ $(PFM)/$(VARIETY)/lockcov: $(PFM)/$(VARIETY)/lockcov.o \
 	$(MPMOBJ)
 
 $(PFM)/$(VARIETY)/mpsicv: $(PFM)/$(VARIETY)/mpsicv.o \
-	$(PFM)/$(VARIETY)/fmtdy.o \
-	$(MPMOBJ) $(AMCOBJ) $(TESTLIBOBJ)
+	$(FMTDYOBJ) $(MPMOBJ) $(AMCOBJ) $(TESTLIBOBJ)
 
 $(PFM)/$(VARIETY)/amcss: $(PFM)/$(VARIETY)/amcss.o \
-	$(PFM)/$(VARIETY)/fmtdy.o \
-	$(MPMOBJ) $(AMCOBJ) $(TESTLIBOBJ)
+	$(FMTDYOBJ) $(MPMOBJ) $(AMCOBJ) $(TESTLIBOBJ)
 
 $(PFM)/$(VARIETY)/amsss: $(PFM)/$(VARIETY)/amsss.o \
-	$(PFM)/$(VARIETY)/fmtdy.o \
-	$(MPMOBJ) $(AMSOBJ) $(TESTLIBOBJ)
+	$(FMTDYOBJ) $(MPMOBJ) $(AMSOBJ) $(TESTLIBOBJ)
 
 $(PFM)/$(VARIETY)/awlut: $(PFM)/$(VARIETY)/awlut.o \
-	$(PFM)/$(VARIETY)/fmtdy.o \
-	$(MPMOBJ) $(LOOBJ) $(AWLOBJ) $(TESTLIBOBJ)
+	$(FMTDYOBJ) $(MPMOBJ) $(LOOBJ) $(AWLOBJ) $(TESTLIBOBJ)
 
 $(PFM)/$(VARIETY)/dwstress: $(PFM)/$(VARIETY)/dwstress.o \
-	$(MPMOBJ) $(AMCOBJ) $(DWOBJ) $(TESTLIBOBJ)
+	$(FMTDYOBJ) $(MPMOBJ) $(AMCOBJ) $(DWOBJ) $(TESTLIBOBJ)
 
 $(PFM)/$(VARIETY)/poolncv: $(PFM)/$(VARIETY)/poolncv.o \
 	$(MPMOBJ) $(TESTLIBOBJ) $(POOLNOBJ) $(ARENAANOBJ)
@@ -377,7 +382,7 @@ ifdef VARIETY
 ifdef TARGET
 # %%PART: Add the dependency file macro for the new part here.
 include $(MPMDEP) $(AMSDEP) $(AMCDEP) $(LODEP) $(SWDEP) \
-	$(AWLDEP) $(DWDEP) $(POOLNDEP) $(ARENAANDEP) $(TESTLIBDEP)
+  $(AWLDEP) $(DWDEP) $(POOLNDEP) $(TESTLIBDEP) $(FMTDYDEP) $(ARENAANDEP)
 endif
 endif
 
diff --git a/mps/src/commpost.nmk b/mps/src/commpost.nmk
index a67f48fb671..5f433ed5239 100644
--- a/mps/src/commpost.nmk
+++ b/mps/src/commpost.nmk
@@ -1,6 +1,6 @@
 # ==== SECOND COMMON FRAGMENT FOR PLATFORMS USING MV AND NMAKE
 #
-# $HopeName: MMsrc!commpost.nmk(trunk.12) $
+# $HopeName: MMsrc!commpost.nmk(trunk.13) $
 # Copyright(C) 1997 Harlequin Group, all rights reserved
 #
 # DESCRIPTION
@@ -74,7 +74,8 @@ variety: $(PFM)\$(VARIETY)\$(TARGET)
 !IFDEF VARIETY
 
 $(PFM)\$(VARIETY)\finalcv.exe: $(PFM)\$(VARIETY)\finalcv.obj \
-	$(MPMOBJ) $(PLINTHOBJ) $(AMCOBJ) $(DWOBJ) $(MRGOBJ) $(TESTLIBOBJ)
+	$(MPMOBJ) $(PLINTHOBJ) $(AMCOBJ) $(DWOBJ) $(DWTESTOBJ) \
+	$(MRGOBJ) $(TESTLIBOBJ)
 
 $(PFM)\$(VARIETY)\mpmconft.exe: $(PFM)\$(VARIETY)\mpmconft.obj \
 	$(MPMOBJ) $(PLINTHOBJ) 
@@ -92,13 +93,16 @@ $(PFM)\$(VARIETY)\qs.exe:  $(PFM)\$(VARIETY)\qs.obj \
 	$(AMCOBJ) $(MPMOBJ) $(PLINTHOBJ) $(TESTLIBOBJ)
 
 $(PFM)\$(VARIETY)\amcss.exe:  $(PFM)\$(VARIETY)\amcss.obj \
-	$(MPMOBJ) $(AMCOBJ) $(PLINTHOBJ) $(DWOBJ) $(TESTLIBOBJ)
+	$(MPMOBJ) $(AMCOBJ) $(PLINTHOBJ) $(DWOBJ) $(DWTESTOBJ) \
+	$(TESTLIBOBJ)
 
 $(PFM)\$(VARIETY)\amsss.exe:  $(PFM)\$(VARIETY)\amsss.obj \
-	$(MPMOBJ) $(AMSOBJ) $(PLINTHOBJ) $(DWOBJ) $(TESTLIBOBJ)
+	$(MPMOBJ) $(AMSOBJ) $(PLINTHOBJ) $(DWOBJ) $(DWTESTOBJ) \
+	$(TESTLIBOBJ)
 
 $(PFM)\$(VARIETY)\mpsicv.exe:  $(PFM)\$(VARIETY)\mpsicv.obj \
-	$(MPMOBJ) $(AMCOBJ) $(PLINTHOBJ) $(DWOBJ) $(TESTLIBOBJ)
+	$(MPMOBJ) $(AMCOBJ) $(PLINTHOBJ) $(DWOBJ) $(DWTESTOBJ) \
+	$(TESTLIBOBJ)
 
 $(PFM)\$(VARIETY)\dwstress.exe:  $(PFM)\$(VARIETY)\dwstress.obj \
 	$(DWOBJ) $(MPMOBJ) $(PLINTHOBJ) $(AMCOBJ)
diff --git a/mps/src/fmtdy.c b/mps/src/fmtdy.c
index aea38faa678..b0fd26bf125 100644
--- a/mps/src/fmtdy.c
+++ b/mps/src/fmtdy.c
@@ -1,6 +1,6 @@
 /* impl.c.fmtdy: DYLAN OBJECT FORMAT IMPLEMENTATION
  *
- *  $HopeName: MMsrc!fmtdy.c(trunk.11) $
+ *  $HopeName: MMsrc!fmtdy.c(trunk.12) $
  *  Copyright (C) 1996,1997 Harlequin Group, all rights reserved.
  *
  *  All objects, B:
@@ -21,20 +21,22 @@
  *
  *  W           WW              pointer to wrapper wrapper
  *  W+1         class           DylanWorks class pointer (traceable)
- *  W+2         (FL << 2) | FF  fixed part length and format
- *  W+3         (VS << 3) | VF  variable part format and element size
- *  W+4         (WT << 2) | 1   tagged pattern vector length
- *  W+5         pattern 0       patterns for fixed part fields
- *  W+5+WT-1    pattern WT-1
+ *  W+2         subtype_mask    DylanWorks subtype_mask (untraceable)
+ *  W+3         (FL << 2) | FF  fixed part length and format
+ *  W+4         (VS << 3) | VF  variable part format and element size
+ *  W+5         (WT << 2) | 1   tagged pattern vector length
+ *  W+6         pattern 0       patterns for fixed part fields
+ *  W+6+WT-1    pattern WT-1
  *
  *  The wrapper wrapper, WW:
  *
  *  WW          WW              WW is it's own wrapper
  *  WW+1        class           DylanWorks class of wrappers
- *  WW+2        (3 << 2) | 2    wrappers have three patterned fields
- *  WW+3        (0 << 3) | 0    wrappers have a non-traceable vector
- *  WW+4        (1 << 2) | 1    one pattern word follows
- *  WW+5        0b001           only field 0 is traceable
+ *  WW+2        subtype_mask    DylanWorks subtype_mask for WW
+ *  WW+3        (4 << 2) | 2    wrappers have four patterned fields
+ *  WW+4        (0 << 3) | 0    wrappers have a non-traceable vector
+ *  WW+5        (1 << 2) | 1    one pattern word follows
+ *  WW+6        0b001           only field 0 is traceable
  *
  *  .improve.abstract.access: There are severe common subexpression
  *  problems.  In particular, code for accessing subfields in the
@@ -72,7 +74,7 @@
 
 #ifndef NDEBUG
 
-static int dylan_wrapper_check(mps_word_t *w)
+int dylan_wrapper_check(mps_word_t *w)
 {
   mps_word_t *ww;
   mps_word_t vh;
@@ -93,34 +95,36 @@ static int dylan_wrapper_check(mps_word_t *w)
    * run-time, it would be possible to know the address of a unique
    * wrapper wrapper and check that instead. */
 
-  assert(w[0] != 0);
-  assert((w[0] & 3) == 0);          /* wrapper wrapper is aligned */
-  ww = (mps_word_t *)w[0];
-  assert(ww[0] == w[0]);            /* wrapper wrapper is own wrapper */
-  assert(ww[1] != 0);               /* wrapper class exists */
-  assert((ww[1] & 3) == 0);         /* wrapper class is aligned */
-  assert(ww[2] == ((3 << 2) | 2));  /* three fields with patterns */
-  assert((ww[3] & 0x00ffffff) == 0);/* non-traceable vector */
-  assert(((ww[3] >> (MPS_WORD_WIDTH - 8)) & 0xff) == 1 ||
-         ((ww[3] >> (MPS_WORD_WIDTH - 8)) & 0xff) == 0); /* version 0 or 1 */
-  assert(ww[4] == ((1 << 2) | 1));  /* one pattern word in wrapper wrapper */
-  assert(ww[5] == 1);               /* first field traceable */
+  assert(w[WW] != 0);
+  assert((w[WW] & 3) == 0);          /* wrapper wrapper is aligned */
+  ww = (mps_word_t *)w[WW];
+  assert(ww[WW] == w[WW]);           /* wrapper wrapper is own wrapper */
+  assert(ww[WC] != 0);               /* wrapper class exists */
+  assert((ww[WC] & 3) == 0);         /* wrapper class is aligned */
+  assert(ww[WF] == (((WS - 1) << 2) | 2));  /* fields with patterns */
+  assert((ww[WV] & 0x00ffffff) == 0);/* non-traceable vector */
+  /* Code in this file only works for version 2 */
+  assert(((ww[WV] >> (MPS_WORD_WIDTH - 8)) & 0xff) == 2);
+  assert(ww[WS] == ((1 << 2) | 1));  /* one pattern word in wrapper wrapper */
+  /* The first field is traceable, the second field can be traced, */
+  /* but doesn't need to be. */
+  assert((ww[WP] == 1) || (ww[WP] == 3));
 
   /* Unpack the wrapper. */
 
-  class = w[1];         /* class */
-  fh = w[2];            /* fixed part header word */
+  class = w[WC];         /* class */
+  fh = w[WF];            /* fixed part header word */
   fl = fh >> 2;         /* fixed part length */
   ff = fh & 3;          /* fixed part format code */
-  vh = w[3];            /* variable part header */
+  vh = w[WV];            /* variable part header */
   version = (vh >> (MPS_WORD_WIDTH - 8)) & 0xff;
-  assert(version == 0 || version == 1);
+  assert(version == 2); /* Code in this file only works for version 2 */
   reserved = (vh >> 8) & 0xff;
   assert(reserved == 0);
   vb = (vh >> 16) & 0xff;
   es = (vh & 0xff) >> 3;/* element size */
   vf = vh & 7;          /* variable part format code */
-  vt = w[4];            /* vector total word (Dylan-tagged) */
+  vt = w[WS];            /* vector total word (Dylan-tagged) */
   t = vt >> 2;          /* vector total length */
 
   /* The second word is the class of the wrapped object. */
@@ -174,7 +178,7 @@ static int dylan_wrapper_check(mps_word_t *w)
   /* The patterns are random bits, so we can't check them.  However, */
   /* the left-over bits in the last pattern should be zero. */
 
-  assert(ff != 2 || (w[4+t] >> ((fh>>2) & (MPS_WORD_WIDTH-1))) == 0);
+  assert(ff != 2 || (w[WS+t] >> ((fh>>2) & (MPS_WORD_WIDTH-1))) == 0);
 
   return 1;
 }
@@ -358,7 +362,7 @@ static mps_res_t dylan_scan1(mps_ss_t mps_ss, mps_addr_t *object_io)
 
   /* Fixed Part */
 
-  fh = w[2];
+  fh = w[WF];
   fl = fh >> 2;                 /* get the fixed part length */
 
   /* It might be worth inlining common cases here, for example, */
@@ -377,7 +381,7 @@ static mps_res_t dylan_scan1(mps_ss_t mps_ss, mps_addr_t *object_io)
       break;
 
       case 2:                   /* patterns */
-      res = dylan_scan_pat(mps_ss, p, q, &w[5], w[4]>>2);
+      res = dylan_scan_pat(mps_ss, p, q, &w[WP], w[WS]>>2);
       if(res) return res;
       break;
 
@@ -389,7 +393,7 @@ static mps_res_t dylan_scan1(mps_ss_t mps_ss, mps_addr_t *object_io)
   }
 
   /* Variable Part */
-  vh = w[3];
+  vh = w[WV];
   vf = vh & 7;                  /* get variable part format */
   if(vf != 7)
   {
@@ -496,7 +500,7 @@ static mps_res_t dylan_scan1_weak(mps_ss_t mps_ss, mps_addr_t *object_io)
 
   ++p;			/* skip header */
 
-  fword = w[2];
+  fword = w[WF];
   fl = fword >> 2;
   /* weak vectors should have at least one fixed field */
   /* (for assoc field) */
@@ -509,7 +513,7 @@ static mps_res_t dylan_scan1_weak(mps_ss_t mps_ss, mps_addr_t *object_io)
 
   assoc = (mps_addr_t *)p[0];
 
-  vword = w[3];
+  vword = w[WV];
   vf = vword & 7;
   vl = (mps_word_t)p[fl] >> 2;
 
@@ -579,9 +583,9 @@ static mps_addr_t dylan_skip(mps_addr_t object)
   assert(dylan_wrapper_check(w));
   ++p;
 
-  p += w[2] >> 2;               /* skip fixed part fields */
+  p += w[WF] >> 2;               /* skip fixed part fields */
 
-  vh = w[3];
+  vh = w[WV];
   vf = vh & 7;                  /* get variable part format */
   if(vf != 7)
   {
@@ -664,7 +668,7 @@ static void dylan_no_fwd(mps_addr_t old, mps_addr_t new)
   notreached();
 }
 
-static void dylan_pad(mps_addr_t addr, size_t size)
+void dylan_pad(mps_addr_t addr, size_t size)
 {
   mps_word_t *p;
 
@@ -715,86 +719,6 @@ mps_fmt_A_s *dylan_fmt_A_weak(void)
   return &dylan_fmt_A_weak_s;
 }
 
-/* Format Test Code */
-
-static mps_word_t *ww = NULL;
-static mps_word_t *tvw;
-
-mps_res_t dylan_init(mps_addr_t addr, size_t size,
-                     mps_addr_t *refs, size_t nr_refs)
-{
-
-  /* Make sure the size is aligned. */
-  assert((size & (ALIGN-1)) == 0);
-
-  if(ww == NULL) {
-    ww = malloc(sizeof(mps_word_t) * 6);
-    if(ww == NULL) return MPS_RES_MEMORY;
-    tvw = malloc(sizeof(mps_word_t) * 5);
-    if(tvw == NULL) {
-      free(ww);
-      return MPS_RES_MEMORY;
-    }
-
-    /* Build a wrapper wrapper. */
-    ww[0] = (mps_word_t)ww;
-    ww[1] = (mps_word_t)ww;     /* dummy class */
-    ww[2] = (3 << 2) | 2;
-    ww[3] = (0 << 3) | 0;
-    ww[4] = (1 << 2) | 1;
-    ww[5] = 1;
-
-    /* Build a wrapper for traceable vectors. */
-    tvw[0] = (mps_word_t)ww;
-    tvw[1] = (mps_word_t)ww;    /* dummy class */
-    tvw[2] = 0;                 /* no fixed part */
-    tvw[3] = 2;                 /* traceable variable part */
-    tvw[4] = 1;                 /* no patterns */
-  }
-
-  /* If there is enough room, make a vector, otherwise just */
-  /* make a padding object. */
-
-  if(size >= sizeof(mps_word_t) * 2) {
-    mps_word_t *p = (mps_word_t *)addr;
-    mps_word_t i, t = (size / sizeof(mps_word_t)) - 2;
-    p[0] = (mps_word_t)tvw;     /* install vector wrapper */
-    p[1] = (t << 2) | 1;        /* tag the vector length */
-    for(i = 0; i < t; ++i)
-      p[2+i] = (mps_word_t)refs[rand() % nr_refs];
-  } else
-    dylan_pad(addr, size);
-
-  return MPS_RES_OK;
-}
-
-void dylan_write(mps_addr_t addr, mps_addr_t *refs, size_t nr_refs)
-{
-  mps_word_t *p = (mps_word_t *)addr;
-
-  /* If the object is a vector, update a random entry. */
-  if(p[0] == (mps_word_t)tvw) {
-    mps_word_t t = p[1] >> 2;
-    if(t > 0)
-      p[2 + (rand() % t)] =
-        (mps_word_t)refs[rand() % nr_refs];
-  }
-}
-
-mps_addr_t dylan_read(mps_addr_t addr)
-{
-  mps_word_t *p = (mps_word_t *)addr;
-
-  /* If the object is a vector, return a random entry. */
-  if(p[0] == (mps_word_t)tvw) {
-    mps_word_t t = p[1] >> 2;
-    if(t > 0)
-      return (mps_addr_t)p[2 + (rand() % t)];
-  }
-
-  return addr;
-}
-
 mps_bool_t dylan_check(mps_addr_t addr)
 {
   assert(addr != 0);
@@ -805,3 +729,4 @@ mps_bool_t dylan_check(mps_addr_t addr)
   unused(addr);
   return 1;
 }
+
diff --git a/mps/src/fmtdy.h b/mps/src/fmtdy.h
index 9d07db25b1f..b4983394494 100644
--- a/mps/src/fmtdy.h
+++ b/mps/src/fmtdy.h
@@ -1,6 +1,6 @@
 /* impl.h.fmtdy: DYLAN OBJECT FORMAT
  *
- * $HopeName: MMsrc!fmtdy.h(trunk.2) $
+ * $HopeName: MMsrc!fmtdy.h(trunk.3) $
  * Copyright (C) 1997 Harlequin Group, all rights reserved
  */
 
@@ -21,5 +21,19 @@ extern void dylan_write(mps_addr_t addr,
                         mps_addr_t *refs, size_t nr_refs);
 extern mps_addr_t dylan_read(mps_addr_t addr);
 extern mps_bool_t dylan_check(mps_addr_t addr);
+extern void dylan_pad(mps_addr_t addr, size_t size);
+extern int dylan_wrapper_check(mps_word_t *w);
+
+#define WW 0
+#define WC 1
+#define WM 2
+#define WF 3
+#define WV 4
+#define WS 5
+#define WP 6
+
+#define BASIC_WRAPPER_SIZE WS
+
+#define ALIGN           sizeof(mps_word_t)
 
 #endif /* fmtdy_h */
diff --git a/mps/src/mps.h b/mps/src/mps.h
index a761558d1a5..fe924f0b402 100644
--- a/mps/src/mps.h
+++ b/mps/src/mps.h
@@ -1,6 +1,6 @@
 /* impl.h.mps: HARLEQUIN MEMORY POOL SYSTEM C INTERFACE
  *
- * $HopeName: MMsrc!mps.h(trunk.26) $
+ * $HopeName: MMsrc!mps.h(trunk.27) $
  * Copyright (C) 1997 The Harlequin Group Limited.  All rights reserved.
  *
  * .readership: customers, MPS developers.
@@ -177,6 +177,10 @@ extern void mps_arena_clamp(mps_arena_t);
 extern void mps_arena_release(mps_arena_t);
 extern void mps_arena_park(mps_arena_t);
 extern mps_res_t mps_arena_collect(mps_arena_t);
+extern void mps_space_clamp(mps_space_t);
+extern void mps_space_release(mps_space_t);
+extern void mps_space_park(mps_space_t);
+extern mps_res_t mps_space_collect(mps_space_t);
 
 extern mps_res_t mps_arena_create(mps_arena_t *, mps_arena_class_t, ...);
 extern mps_res_t mps_arena_create_v(mps_arena_t *, mps_arena_class_t, va_list);
diff --git a/mps/src/mpsi.c b/mps/src/mpsi.c
index f7379792446..8d708f02e4c 100644
--- a/mps/src/mpsi.c
+++ b/mps/src/mpsi.c
@@ -1,6 +1,6 @@
 /* impl.c.mpsi: MEMORY POOL SYSTEM C INTERFACE LAYER
  *
- * $HopeName: MMsrc!mpsi.c(trunk.31) $
+ * $HopeName: MMsrc!mpsi.c(trunk.32) $
  * Copyright (C) 1997 The Harlequin Group Limited.  All rights reserved.
  *
  * .purpose: This code bridges between the MPS interface to C,
@@ -52,7 +52,7 @@
 #include "mps.h"
 #include "mpsavm.h" /* only for mps_space_create */
 
-SRCID(mpsi, "$HopeName: MMsrc!mpsi.c(trunk.31) $");
+SRCID(mpsi, "$HopeName: MMsrc!mpsi.c(trunk.32) $");
 
 
 /* mpsi_check -- check consistency of interface mappings
@@ -213,6 +213,7 @@ size_t mps_space_committed(mps_space_t mps_space)
   return mps_arena_committed(mps_space);
 }
 
+
 void mps_arena_clamp(mps_arena_t mps_arena)
 {
   Arena arena = (Arena)mps_arena;
@@ -220,7 +221,14 @@ void mps_arena_clamp(mps_arena_t mps_arena)
   ArenaClamp(arena);
   ArenaLeave(arena);
 }
+
+/* for backward compatibility */
+void mps_space_clamp(mps_space_t mps_space)
+{
+  mps_arena_clamp(mps_space);
+}
  
+   
 void mps_arena_release(mps_arena_t mps_arena)
 {
   Arena arena = (Arena)mps_arena;
@@ -228,7 +236,14 @@ void mps_arena_release(mps_arena_t mps_arena)
   ArenaRelease(arena);
   ArenaLeave(arena);
 }
- 
+
+/* for backward compatibility */
+void mps_space_release(mps_space_t mps_space)
+{
+  mps_arena_release(mps_space);
+}
+  
+
 void mps_arena_park(mps_space_t mps_space)
 {
   Arena arena = (Arena)mps_space;
@@ -236,7 +251,14 @@ void mps_arena_park(mps_space_t mps_space)
   ArenaPark(arena);
   ArenaLeave(arena);
 }
+
+/* for backward compatibility */
+void mps_space_park(mps_space_t mps_space)
+{
+  mps_arena_park(mps_space);
+}
  
+
 mps_res_t mps_arena_collect(mps_space_t mps_space)
 {
   Res res;
@@ -246,7 +268,13 @@ mps_res_t mps_arena_collect(mps_space_t mps_space)
   ArenaLeave(arena);
   return res;
 }
- 
+
+/* for backward compatibility */
+mps_res_t mps_space_collect(mps_space_t mps_space)
+{
+  return mps_arena_collect(mps_space);
+}
+    
 
 /* mps_arena_create -- create an arena object */
 
diff --git a/mps/src/poolawl.c b/mps/src/poolawl.c
index dd351a31df1..b8086c9af23 100644
--- a/mps/src/poolawl.c
+++ b/mps/src/poolawl.c
@@ -1,6 +1,6 @@
 /* impl.c.poolawl: AUTOMATIC WEAK LINKED POOL CLASS
  *
- * $HopeName: MMsrc!poolawl.c(trunk.21) $
+ * $HopeName: MMsrc!poolawl.c(trunk.22) $
  * Copyright (C) 1997 The Harlequin Group Limited.  All rights reserved.
  *
  * READERSHIP
@@ -16,7 +16,7 @@
 #include "mpm.h"
 #include "mpscawl.h"
 
-SRCID(poolawl, "$HopeName: MMsrc!poolawl.c(trunk.21) $");
+SRCID(poolawl, "$HopeName: MMsrc!poolawl.c(trunk.22) $");
 
 
 #define AWLSig	((Sig)0x519b7a37)	/* SIGPooLAWL */
@@ -422,7 +422,7 @@ static Bool AWLDependentObject(Addr *objReturn, Addr parent)
   AVER(wrapper[0] != 0);
   /* check wrapper wrapper is wrapper wrapper wrapper */
   AVER(wrapper[0] == ((Word *)wrapper[0])[0]);
-  fword = wrapper[2];
+  fword = wrapper[3];
   ff = fword & 3;
   /* Traceable Fixed part */
   AVER(ff == 1);
diff --git a/mps/src/poolmrg.c b/mps/src/poolmrg.c
index c6f44b9f509..42991794a71 100644
--- a/mps/src/poolmrg.c
+++ b/mps/src/poolmrg.c
@@ -2,7 +2,7 @@
  * 
  * MANUAL RANK GUARDIAN POOL
  * 
- * $HopeName: MMsrc!poolmrg.c(trunk.17) $
+ * $HopeName: MMsrc!poolmrg.c(trunk.18) $
  * Copyright (C) 1997 The Harlequin Group Limited.  All rights reserved.
  *
  * READERSHIP
@@ -26,7 +26,7 @@
 #include "mpm.h"
 #include "poolmrg.h"
 
-SRCID(poolmrg, "$HopeName: MMsrc!poolmrg.c(trunk.17) $");
+SRCID(poolmrg, "$HopeName: MMsrc!poolmrg.c(trunk.18) $");
 
 
 /* Types */
@@ -446,18 +446,19 @@ static Res MRGGroupScan(ScanState ss, MRGGroup group, MRG mrg)
     for(i=0; i < nGuardians; ++i) {
       refPart = refPartOfIndex(group, i);
 
-      /* Not worth checking whether the reference is free, because */
-      /* the zone check will discard that case cheaply. */
-
-      /* .ref.direct: We can access the reference directly */
-      /* because we are in a scan and the shield is exposed. */
-      if(TRACE_FIX1(ss, refPart->ref)) {
-        res = TRACE_FIX2(ss, &(refPart->ref));
-        if(res != ResOK) 
-          return res;
-      
-        if(ss->rank == RankFINAL && !ss->wasMarked) { /* .improve.rank */
-          MRGFinalize(arena, group, i);
+      /* free guardians are not scanned */
+      if(MRGLinkOfRefPart(refPart, arena)->state != MRGGuardianFREE) {
+	ss->wasMarked = TRUE;
+	/* .ref.direct: We can access the reference directly */
+	/* because we are in a scan and the shield is exposed. */
+	if(TRACE_FIX1(ss, refPart->ref)) {
+	  res = TRACE_FIX2(ss, &(refPart->ref));
+	  if(res != ResOK) 
+	    return res;
+	
+	  if(ss->rank == RankFINAL && !ss->wasMarked) { /* .improve.rank */
+	    MRGFinalize(arena, group, i);
+	  }
 	}
       }
     }
diff --git a/mps/src/sso1al.s b/mps/src/sso1al.s
index e9594764c73..8ade1783d61 100644
--- a/mps/src/sso1al.s
+++ b/mps/src/sso1al.s
@@ -1,16 +1,16 @@
  # impl.s.sso1al: STACK SCANNING FOR DIGITAL UNIX / ALPHA
  #
- # $HopeName$
+ # $HopeName: MMsrc!sso1al.s(trunk.1) $
  # Copyright (C) 1997 Harlequin Group, all rights reserved
  #
  # .readership: Any MPS developer that is prepared to read Alpha
  # assembly code in DIGITAL UNIX 'as' syntax.
  #
- # See design.mps.sso1al for the design.
+ # See design.mps.sso1al for the design (exists).
 
 
 .globl	StackScan
-.globl	TraceScanAreaTagged
+.globl	TraceScanArea
 
 .ent	StackScan
 StackScan:
@@ -28,13 +28,13 @@ stq	$14,48($sp)
 stq	$15,56($sp)
 .prologue	1
 
- # bis $31,$16,$16 1st arg to TraceScanAreaTagged is same as our 1st arg
+ # bis $31,$16,$16 1st arg to TraceScanArea is same as our 1st arg
 bis	$31,$17,$18	# area to be scanned is from $sp to StackBot
 bis	$31,$sp,$17
 
-jsr	$26,TraceScanAreaTagged
+jsr	$26,TraceScanArea
 ldgp	$gp,0($26)
- # our result is TraceScanAreaTagged's result, so leave $0 untouched
+ # our result is TraceScanArea's result, so leave $0 untouched
 
 ldq	$26,0($sp)
 lda	$sp,+64($sp)
diff --git a/mps/src/w3i3mv.nmk b/mps/src/w3i3mv.nmk
index f5bd5f65193..4dfb85a14db 100644
--- a/mps/src/w3i3mv.nmk
+++ b/mps/src/w3i3mv.nmk
@@ -1,6 +1,6 @@
 # ==== NTI3MV NMAKE FILE ====
 #
-# $HopeName: MMsrc!w3i3mv.nmk(trunk.44) $
+# $HopeName: MMsrc!w3i3mv.nmk(trunk.45) $
 #
 # Copyright (C) 1995,1996,1997 Harlequin Group, all rights reserved
 #
@@ -25,6 +25,7 @@ AMS = <poolams>
 AWL = <poolawl>
 LO = <lo>
 DW  = <fmtdy>
+DWTEST = <fmtdytst>
 POOLN = <pooln>
 ARENAAN = <arenaan>
 TESTLIB = <testlib>
@@ -62,6 +63,8 @@ LOOBJ0 = $(LO:<=w3i3mv\he\)
 LOOBJ = $(LOOBJ0:>=.obj)
 DWOBJ0 = $(DW:<=w3i3mv\he\)
 DWOBJ = $(DWOBJ0:>=.obj)
+DWTESTOBJ0 = $(DWTEST:<=w3i3mv\he\)
+DWTESTOBJ = $(DWTESTOBJ0:>=.obj)
 POOLNOBJ0 = $(POOLN:<=w3i3mv\he\)
 POOLNOBJ = $(POOLNOBJ0:>=.obj)
 ARENAANOBJ0 = $(ARENAAN:<=w3i3mv\he\)
@@ -89,6 +92,8 @@ LOOBJ0 = $(LO:<=w3i3mv\ce\)
 LOOBJ = $(LOOBJ0:>=.obj)
 DWOBJ0 = $(DW:<=w3i3mv\ce\)
 DWOBJ = $(DWOBJ0:>=.obj)
+DWTESTOBJ0 = $(DWTEST:<=w3i3mv\ce\)
+DWTESTOBJ = $(DWTESTOBJ0:>=.obj)
 POOLNOBJ0 = $(POOLN:<=w3i3mv\ce\)
 POOLNOBJ = $(POOLNOBJ0:>=.obj)
 ARENAANOBJ0 = $(ARENAAN:<=w3i3mv\ce\)
@@ -116,6 +121,8 @@ LOOBJ0 = $(LO:<=w3i3mv\hi\)
 LOOBJ = $(LOOBJ0:>=.obj)
 DWOBJ0 = $(DW:<=w3i3mv\hi\)
 DWOBJ = $(DWOBJ0:>=.obj)
+DWTESTOBJ0 = $(DWTEST:<=w3i3mv\hi\)
+DWTESTOBJ = $(DWTESTOBJ0:>=.obj)
 POOLNOBJ0 = $(POOLN:<=w3i3mv\hi\)
 POOLNOBJ = $(POOLNOBJ0:>=.obj)
 ARENAANOBJ0 = $(ARENAAN:<=w3i3mv\hi\)
@@ -143,6 +150,8 @@ LOOBJ0 = $(LO:<=w3i3mv\ci\)
 LOOBJ = $(LOOBJ0:>=.obj)
 DWOBJ0 = $(DW:<=w3i3mv\ci\)
 DWOBJ = $(DWOBJ0:>=.obj)
+DWTESTOBJ0 = $(DWTEST:<=w3i3mv\ci\)
+DWTESTOBJ = $(DWTESTOBJ0:>=.obj)
 POOLNOBJ0 = $(POOLN:<=w3i3mv\ci\)
 POOLNOBJ = $(POOLNOBJ0:>=.obj)
 ARENAANOBJ0 = $(ARENAAN:<=w3i3mv\ci\)
@@ -170,6 +179,8 @@ LOOBJ0 = $(LO:<=w3i3mv\ti\)
 LOOBJ = $(LOOBJ0:>=.obj)
 DWOBJ0 = $(DW:<=w3i3mv\ti\)
 DWOBJ = $(DWOBJ0:>=.obj)
+DWTESTOBJ0 = $(DWTEST:<=w3i3mv\ti\)
+DWTESTOBJ = $(DWTESTOBJ0:>=.obj)
 POOLNOBJ0 = $(POOLN:<=w3i3mv\ti\)
 POOLNOBJ = $(POOLNOBJ0:>=.obj)
 ARENAANOBJ0 = $(ARENAAN:<=w3i3mv\ti\)
@@ -197,6 +208,8 @@ LOOBJ0 = $(LO:<=w3i3mv\wi\)
 LOOBJ = $(LOOBJ0:>=.obj)
 DWOBJ0 = $(DW:<=w3i3mv\wi\)
 DWOBJ = $(DWOBJ0:>=.obj)
+DWTESTOBJ0 = $(DWTEST:<=w3i3mv\wi\)
+DWTESTOBJ = $(DWTESTOBJ0:>=.obj)
 POOLNOBJ0 = $(POOLN:<=w3i3mv\wi\)
 POOLNOBJ = $(POOLNOBJ0:>=.obj)
 ARENAANOBJ0 = $(ARENAAN:<=w3i3mv\wi\)