diff --git a/mps/code/zumr.c b/mps/code/zumr.c
index d8129ef50f6..e85d802cc9d 100644
--- a/mps/code/zumr.c
+++ b/mps/code/zumr.c
@@ -1,4 +1,4 @@
-/* zcoll.c: Collection test
+/* zumr.c: UnManaged References test
  *
  * $Id$
  * Copyright (c) 2008 Ravenbrook Limited.  See end of file for license.
@@ -88,422 +88,41 @@ static mps_gen_param_s testChain[genCOUNT] = {
  */
 #define myrootCOUNT 30000
 static void *myroot[myrootCOUNT];
+static void *myunmanaged[10];
 
-
-static unsigned long cols(size_t bytes)
-{
-  double M;  /* Mebibytes */
-  unsigned long cM;  /* hundredths of a Mebibyte */
-
-  M = (double)bytes / (1UL<<20);
-  cM = (unsigned long)(M * 100 + 0.5);  /* round to nearest */
-  return cM;
-}
-
-/* showStatsAscii -- present collection stats, 'graphically'
- *
+/* testscriptC -- do stuff
  */
-static void showStatsAscii(size_t notcon, size_t con, size_t live, size_t alimit)
-{
-  int n = cols(notcon);
-  int c = cols(notcon + con);
-  int l = cols(notcon + live);  /* a fraction of con */
-  int a = cols(alimit);
-  int count;
-  int i;
-  
-  /* if we can show alimit within 200 cols, do so */
-  count = (a < 200) ? a + 1 : c;
-  
-  for(i = 0; i < count; i++) {
-    printf( (i == a)  ? "A"
-            : (i < n) ? "n"
-            : (i < l) ? "L"
-            : (i < c) ? "_"
-            : " "
-          );
-  }
-  printf("\n");
-}
-
-
-/* print_M -- print count of bytes as Mebibytes with decimal fraction 
- *
- * Input:   208896
- * Output:  0m199
- */
-static void print_M(size_t bytes)
-{
-  size_t M;  /* Mebibytes */
-  double Mfrac;  /* fraction of a Mebibyte */
-
-  M = bytes / (1UL<<20);
-  Mfrac = (double)(bytes % (1UL<<20));
-  Mfrac = (Mfrac / (1UL<<20));
-
-  printf("%1lum%03.f", M, Mfrac * 1000);
-}
-
-
-/* showStatsText -- present collection stats
- *
- * prints:
- *   Coll End  0m137[->0m019 14%-live] (0m211-not )
- */
-static void showStatsText(size_t notcon, size_t con, size_t live)
-{
-  double liveFrac = (double)live / (double)con;
-
-  print_M(con);
-  printf("[->");
-  print_M(live);
-  printf("% 3.f%%-live]", liveFrac * 100);
-  printf(" (");
-  print_M(notcon);
-  printf("-not ");
-  printf(")\n");
-}
-
-/* get -- get messages
- *
- */
-static void get(mps_arena_t arena)
-{
-  mps_message_type_t type;
-
-  while (mps_message_queue_type(&type, arena)) {
-    mps_message_t message;
-    static mps_clock_t mclockBegin = 0;
-    static mps_clock_t mclockEnd = 0;
-    mps_word_t *obj;
-    mps_word_t objind;
-    mps_addr_t objaddr;
-
-    cdie(mps_message_get(&message, arena, type),
-         "get");
-    
-    switch(type) {
-      case mps_message_type_gc_start(): {
-        mclockBegin = mps_message_clock(arena, message);
-        printf("    %5lu: (%5lu)",
-               mclockBegin, mclockBegin - mclockEnd);
-        printf("    Coll Begin                                     (%s)\n",
-               mps_message_gc_start_why(arena, message));
-        break;
-      }
-      case mps_message_type_gc(): {
-        size_t con = mps_message_gc_condemned_size(arena, message);
-        size_t notcon = mps_message_gc_not_condemned_size(arena, message);
-        /* size_t other = 0;  -- cannot determine; new method reqd */
-        size_t live = mps_message_gc_live_size(arena, message);
-        size_t alimit = mps_arena_reserved(arena);
-
-        mclockEnd = mps_message_clock(arena, message);
-        
-        printf("    %5lu: (%5lu)",
-               mclockEnd, mclockEnd - mclockBegin);
-        printf("    Coll End  ");
-        showStatsText(notcon, con, live);
-        if(rnd()==0) showStatsAscii(notcon, con, live, alimit);
-        break;
-      }
-      case mps_message_type_finalization(): {
-        mps_message_finalization_ref(&objaddr, arena, message);
-        obj = objaddr;
-        objind = DYLAN_INT_INT(DYLAN_VECTOR_SLOT(obj, 0));
-        printf("    Finalization for object %lu at %p\n", objind, objaddr);
-        break;
-      }
-      default: {
-        cdie(0, "message type");
-        break;
-      }
-    }
-    
-    mps_message_discard(arena, message);
-  }
-}
-
-
-/* .catalog: The Catalog client:
- * 
- * This is an MPS client for testing the MPS.  It simulates 
- * converting a multi-page "Catalog" document from a page-description 
- * into a bitmap.
- *
- * The intention is that this task will cause memory usage that is 
- * fairly realistic (much more so than randomly allocated objects 
- * with random interconnections.  The patterns in common with real 
- * clients are:
- *   - the program input and its task are 'fractal', with a 
- *     self-similar hierarchy;
- *   - object allocation is prompted by each successive element of 
- *     the input/task;
- *   - objects are often used to store a transformed version of the 
- *     program input;
- *   - there may be several stages of transformation;
- *   - at each stage, the old object (holding the untransformed data) 
- *     may become dead;
- *   - sometimes a tree of objects becomes dead once an object at 
- *     some level of the hierarchy has been fully processed;
- *   - there is more than one hierarchy, and objects in different 
- *     hierarchies interact.
- *
- * The entity-relationship diagram is:
- *        Catalog -< Page -< Article -< Polygon
- *                                        v
- *                                        |
- *        Palette --------------------< Colour
- *
- * The first hierarchy is a Catalog, containing Pages, each 
- * containing Articles (bits of artwork etc), each composed of 
- * Polygons.  Each polygon has a single colour.  
- *
- * The second hierarchy is a top-level Palette, containing Colours.  
- * Colours (in this client) are expensive, large objects (perhaps 
- * because of complex colour modelling or colour blending).
- *
- * The things that matter for their effect on MPS behaviour are:
- *   - when objects are allocated, and how big they are;
- *   - how the reference graph mutates over time;
- *   - how the mutator accesses objects (barrier hits).
- */
-
-enum {
-  CatalogRootIndex = 0,
-  CatalogSig = 0x0000CA2A,  /* CATAlog */
-  CatalogFix = 1,
-  CatalogVar = 10,
-  PageSig =    0x0000BA9E,  /* PAGE */
-  PageFix = 1,
-  PageVar = 100,
-  ArtSig =     0x0000A621,  /* ARTIcle */
-  ArtFix = 1,
-  ArtVar = 100,
-  PolySig =    0x0000B071,  /* POLYgon */
-  PolyFix = 1,
-  PolyVar = 100
-};
-
-static void CatalogCheck(void)
-{
-  mps_word_t w;
-  void *Catalog, *Page, *Art, *Poly;
-  unsigned long Catalogs = 0, Pages = 0, Arts = 0, Polys = 0;
-  int i, j, k;
-
-  /* retrieve Catalog from root */
-  Catalog = myroot[CatalogRootIndex];
-  if(!Catalog)
-    return;
-  Insist(DYLAN_VECTOR_SLOT(Catalog, 0) == DYLAN_INT(CatalogSig));
-  Catalogs += 1;
-
-  for(i = 0; i < CatalogVar; i += 1) {
-    /* retrieve Page from Catalog */
-    w = DYLAN_VECTOR_SLOT(Catalog, CatalogFix + i);
-    /* printf("Page = 0x%8x\n", (unsigned int) w); */
-    if(w == DYLAN_INT(0))
-      break;
-    Page = (void *)w;
-    Insist(DYLAN_VECTOR_SLOT(Page, 0) == DYLAN_INT(PageSig));
-    Pages += 1;
-    
-    for(j = 0; j < PageVar; j += 1) {
-      /* retrieve Art from Page */
-      w = DYLAN_VECTOR_SLOT(Page, PageFix + j);
-      if(w == DYLAN_INT(0))
-        break;
-      Art = (void *)w;
-      Insist(DYLAN_VECTOR_SLOT(Art, 0) = DYLAN_INT(ArtSig));
-      Arts += 1;
-
-      for(k = 0; k < ArtVar; k += 1) {
-        /* retrieve Poly from Art */
-        w = DYLAN_VECTOR_SLOT(Art, ArtFix + k);
-        if(w == DYLAN_INT(0))
-          break;
-        Poly = (void *)w;
-        Insist(DYLAN_VECTOR_SLOT(Poly, 0) = DYLAN_INT(PolySig));
-        Polys += 1;
-      }
-    }
-  }
-  printf("Catalog ok with: Catalogs: %lu, Pages: %lu, Arts: %lu, Polys: %lu.\n",
-         Catalogs, Pages, Arts, Polys);
-}
-
-
-/* CatalogDo -- make a Catalog and its tree of objects
- *
- * .catalog.broken: this code, when compiled with 
- * moderate optimization, may have ambiguous interior pointers but 
- * lack corresponding ambiguous base pointers to MPS objects.  This 
- * means the interior pointers are unmanaged references, and the 
- * code goes wrong.  The hack in poolamc.c#4 cures this, but not very 
- * nicely.  For further discussion, see:
- *    <http://info.ravenbrook.com/mail/2009/02/05/18-05-52/0.txt>
- */
-static void CatalogDo(mps_arena_t arena, mps_ap_t ap)
+static void testscriptC(mps_arena_t arena, mps_ap_t ap, mps_root_t root_stackreg)
 {
   mps_word_t v;
-  void *Catalog, *Page, *Art, *Poly;
-  int i, j, k;
+  enum {thingSig = 0x00007770 >> 2};
 
-  die(make_dylan_vector(&v, ap, CatalogFix + CatalogVar), "Catalog");
-  DYLAN_VECTOR_SLOT(v, 0) = DYLAN_INT(CatalogSig);
-  Catalog = (void *)v;
+  printf("  U1()\n");
+  die(make_dylan_vector(&v, ap, 1), "make_dylan_vector");
+  DYLAN_VECTOR_SLOT(v, 0) = DYLAN_INT(thingSig);
+  myroot[0] = (void*)v;
+  printf("myroot[0] = %p\n", myroot[0]);
+  Insist(DYLAN_VECTOR_SLOT(myroot[0], 0) = DYLAN_INT(thingSig));
   
-  /* store Catalog in root */
-  myroot[CatalogRootIndex] = Catalog;
-  get(arena);
-
-  fflush(stdout);
-  CatalogCheck();
-
-  for(i = 0; i < CatalogVar; i += 1) {
-    die(make_dylan_vector(&v, ap, PageFix + PageVar), "Page");
-    DYLAN_VECTOR_SLOT(v, 0) = DYLAN_INT(PageSig);
-    Page = (void *)v;
-
-    /* store Page in Catalog */
-    DYLAN_VECTOR_SLOT(Catalog, CatalogFix + i) = (mps_word_t)Page;
-    get(arena);
-    
-    printf("Page %d: make articles\n", i);
-    fflush(stdout);
-    
-    for(j = 0; j < PageVar; j += 1) {
-      die(make_dylan_vector(&v, ap, ArtFix + ArtVar), "Art");
-      DYLAN_VECTOR_SLOT(v, 0) = DYLAN_INT(ArtSig);
-      Art = (void *)v;
-
-      /* store Art in Page */
-      DYLAN_VECTOR_SLOT(Page, PageFix + j) = (mps_word_t)Art;
-      get(arena);
-
-      for(k = 0; k < ArtVar; k += 1) {
-        die(make_dylan_vector(&v, ap, PolyFix + PolyVar), "Poly");
-        DYLAN_VECTOR_SLOT(v, 0) = DYLAN_INT(PolySig);
-        Poly = (void *)v;
-
-        /* store Poly in Art */
-        DYLAN_VECTOR_SLOT(Art, ArtFix + k) = (mps_word_t)Poly;
-        /* get(arena); */
-      }
-    }
-  }
-  fflush(stdout);
-  CatalogCheck();
+  /* Ru */
+  myunmanaged[0] = myroot[0];
+  printf("myunmanaged[0] = %p\n", myunmanaged[0]);
+  Insist(DYLAN_VECTOR_SLOT(myunmanaged[0], 0) = DYLAN_INT(thingSig));
+  
+  /* Flip */
+  v = 0;
+  mps_root_destroy(root_stackreg);
+  mps_arena_collect(arena);
+  
+  /* Ra */
+  printf("myroot[0] = %p\n", myroot[0]);
+  printf("myunmanaged[0] = %p\n", myunmanaged[0]);
+  Insist(DYLAN_VECTOR_SLOT(myroot[0], 0) = DYLAN_INT(thingSig));
+  Insist(DYLAN_VECTOR_SLOT(myunmanaged[0], 0) = DYLAN_INT(thingSig));
 }
 
 
-/* checksi -- check count of sscanf items is correct
- */
-
-static void checksi(int si, int si_shouldBe, const char *script, const char *scriptAll)
-{
-  if(si != si_shouldBe) {
-    printf("bad script command %s (full script %s).\n", script, scriptAll);
-    cdie(FALSE, "unknown script command");
-  }
-}
-
-/* testscriptC -- actually runs a test script
- *
- */
-static void testscriptC(mps_arena_t arena, mps_ap_t ap, const char *script)
-{
-  const char *scriptAll = script;
-  const char *cmd;
-  int si, sb;  /* sscanf items, sscanf bytes */
-
-  while(*script != '\0') {
-    do {  /* to allow break */
-      cmd = "Collect";
-      if(0 == strncmp(script, cmd, strlen(cmd))) {
-        si = sscanf(script, "Collect%n",
-                       &sb);
-        checksi(si, 0, script, scriptAll);
-        script += sb;
-        printf("  Collect\n");
-        mps_arena_collect(arena);
-        break;
-      }
-
-      cmd = "Katalog";
-      if(0 == strncmp(script, cmd, strlen(cmd))) {
-        si = sscanf(script, "Katalog()%n",
-                       &sb);
-        checksi(si, 0, script, scriptAll);
-        script += sb;
-        printf("  Katalog()\n");
-        CatalogDo(arena, ap);
-        break;
-      }
-
-      cmd = "Make";
-      if(0 == strncmp(script, cmd, strlen(cmd))) {
-        unsigned keepCount = 0;
-        unsigned long objCount = 0;
-        unsigned keepTotal = 0;
-        unsigned keep1in = 0;
-        unsigned keepRootspace = 0;
-        si = sscanf(script, "Make(keep-1-in %u, keep %u, rootspace %u)%n",
-                    &keep1in, &keepTotal, &keepRootspace, &sb);
-        checksi(si, 3, script, scriptAll);
-        script += sb;
-        printf("  Make(keep-1-in %u, keep %u, rootspace %u).\n",
-               keep1in, keepTotal, keepRootspace);
-        
-        Insist(keepRootspace <= myrootCOUNT);
-
-        objCount = 0;
-        while(keepCount < keepTotal) {
-          mps_word_t v;
-          die(make_dylan_vector(&v, ap, 2), "make_dylan_vector");
-          DYLAN_VECTOR_SLOT(v, 0) = DYLAN_INT(objCount);
-          DYLAN_VECTOR_SLOT(v, 1) = (mps_word_t)NULL;
-          objCount++;
-          if(rnd() % keep1in == 0) {
-            /* keep this one */
-            myroot[rnd() % keepRootspace] = (void*)v;
-            keepCount++;
-          }
-          get(arena);
-        }
-        printf("  ...made and kept: %u objects, storing cyclically in "
-               "first %u roots "
-               "(actually created %lu objects, in accord with "
-               "keep-1-in %u).\n",
-               keepCount, keepRootspace, objCount, keep1in);
-
-        break;
-      }
-      
-      if(*script == ' '
-         || *script == ','
-         || *script == '.') {
-        script++;
-        break;
-      }
-      
-      /* default: */
-      {
-        printf("unknown script command %c (script %s).\n",
-               *script, scriptAll);
-        cdie(FALSE, "unknown script command");
-        return;
-      }
-    } while(0);
-    
-    get(arena);
-  }
-
-}
-
-
-/* testscriptB -- create pools and objects; call testscriptC
+/* testscriptB -- create pools and objects
  *
  * Is called via mps_tramp, so matches mps_tramp_t function prototype,
  * and use trampDataStruct to pass parameters.
@@ -559,9 +178,9 @@ static void *testscriptB(void *arg, size_t s)
   mps_message_type_enable(arena, mps_message_type_gc());
   mps_message_type_enable(arena, mps_message_type_finalization());
 
-  testscriptC(arena, ap, script);
+  testscriptC(arena, ap, root_stackreg);
 
-  mps_root_destroy(root_stackreg);
+  /* mps_root_destroy(root_stackreg); -- destroyed in testscriptC */
   mps_ap_destroy(ap);
   mps_root_destroy(root_table);
   mps_pool_destroy(amc);
@@ -620,15 +239,8 @@ int main(int argc, char **argv)
 
   randomize(argc, argv);
 
-  /* The most basic scripts */
-
-  /* 1<<19 == 524288 == 1/2 Mebibyte */
-  testscriptA("Arena(size 524288), Make(keep-1-in 5, keep 50000, rootspace 30000), Collect.");
-
-  /* 16<<20 == 16777216 == 16 Mebibyte */
-  /* See .catalog.broken.
-  testscriptA("Arena(size 16777216), Katalog(), Collect.");
-  */
+  /* test unmanaged */
+  testscriptA("Arena(size 524288), U1().");
 
   fflush(stdout); /* synchronize */
   fprintf(stderr, "\nConclusion:  Failed to find any defects.\n");