diff --git a/mps/src/amcsshe.c b/mps/src/amcsshe.c
new file mode 100644
index 00000000000..92b136469c4
--- /dev/null
+++ b/mps/src/amcsshe.c
@@ -0,0 +1,288 @@
+/* impl.c.amcsshe: POOL CLASS AMC STRESS TEST WITH HEADER
+ *
+ * $HopeName$
+ * Copyright (C) 2000 Harlequin Limited.  All rights reserved.
+ */
+
+#include "fmthe.h"
+#include "testlib.h"
+
+#include "mpscamc.h"
+#include "mpsavm.h"
+#include "mpstd.h"
+#ifdef MPS_OS_W3
+#include "mpsw3.h"
+#endif
+#include "mps.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+
+#define testArenaSIZE     ((size_t)64<<20)
+#define avLEN             3
+#define exactRootsCOUNT   300
+#define ambigRootsCOUNT   50
+#define collectionsCOUNT  18
+#define rampSIZE          5
+#define initTestFREQ      6000
+/* objNULL needs to be odd so that it's ignored in exactRoots. */
+#define objNULL           ((mps_addr_t)0xDECEA5ED)
+
+
+static mps_pool_t pool;
+static mps_ap_t ap;
+static mps_addr_t exactRoots[exactRootsCOUNT];
+static mps_addr_t ambigRoots[ambigRootsCOUNT];
+
+
+
+static mps_word_t *ww = NULL;
+static mps_word_t *tvw;
+
+
+static mps_word_t dylan_make_WV(mps_word_t version, mps_word_t vb,
+                                mps_word_t es, mps_word_t vf) 
+{
+  /* VERSION- ... VB------ reserved ES---VF- */
+  return((version << (MPS_WORD_WIDTH - 8)) |
+	 (vb << 16) |
+	 (es << 3) |
+	 vf);
+}
+
+
+static mps_res_t init(mps_addr_t addr, size_t size,
+                      mps_addr_t *refs, size_t nr_refs)
+{
+
+  /* Make sure the size is aligned. */
+  if ((size & (ALIGN-1)) != 0) return MPS_RES_PARAM;
+
+  if(ww == NULL) {
+    ww = malloc(sizeof(mps_word_t) * (BASIC_WRAPPER_SIZE + 1));
+    if(ww == NULL) return MPS_RES_MEMORY;
+    tvw = malloc(sizeof(mps_word_t) * BASIC_WRAPPER_SIZE);
+    if(tvw == NULL) {
+      free(ww);
+      return MPS_RES_MEMORY;
+    }
+
+    /* Build a wrapper wrapper. */
+    ww[WW] = (mps_word_t)ww;
+    ww[WC] = (mps_word_t)ww;     /* dummy class */
+    ww[WM] = (1 << 2) | 1;       /* dummy subtype_mask */
+    ww[WF] = ((WS - 1) << 2) | 2;
+    ww[WV] = dylan_make_WV(2, 0, 0, 0);
+    ww[WS] = (1 << 2) | 1;
+    ww[WP] = 1;
+
+    /* Build a wrapper for traceable vectors. */
+    tvw[WW] = (mps_word_t)ww;
+    tvw[WC] = (mps_word_t)ww;    /* dummy class */
+    tvw[WM] = (1 << 2) | 1;      /* dummy subtype_mask */
+    tvw[WF] = 0;                 /* no fixed part */
+    tvw[WV] = dylan_make_WV(2, 0, 0, 2); /* traceable variable part */
+    tvw[WS] = 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) {
+      mps_word_t r = rnd();
+
+      if(r & 1)
+        p[2+i] = ((r & ~(mps_word_t)3) | 1); /* random int */
+      else
+        p[2+i] = (mps_word_t)refs[(r >> 1) % nr_refs]; /* random ptr */
+    }
+  } else {
+    die(MPS_RES_FAIL, "small object");
+  }
+
+  return MPS_RES_OK;
+}
+
+
+static void dylan_write(mps_addr_t addr, mps_addr_t *refs, size_t nr_refs)
+{
+  mps_word_t *p = (mps_word_t *)addr;
+  mps_word_t t = p[1] >> 2;
+
+  /* If the object is a vector, update a random entry. */
+  if(p[0] == (mps_word_t)tvw && t > 0) {
+    mps_word_t r = rnd();
+    size_t i = 2 + (rnd() % t);
+
+    if(r & 1)
+      p[i] = ((r & ~(mps_word_t)3) | 1); /* random int */
+    else
+      p[i] = (mps_word_t)refs[(r >> 1) % nr_refs]; /* random ptr */
+  }
+}
+
+
+static mps_addr_t make(void)
+{
+  size_t length = rnd() % (2*avLEN);
+  size_t size = (length+2) * sizeof(mps_word_t);
+  mps_addr_t p, userP;
+  mps_res_t res;
+
+  do {
+    MPS_RESERVE_BLOCK(res, p, ap, size + headerSIZE);
+    if(res)
+      die(res, "MPS_RESERVE_BLOCK");
+    userP = (mps_addr_t)((char*)p + headerSIZE);
+    res = init(userP, size, exactRoots, exactRootsCOUNT);
+    if(res)
+      die(res, "dylan_init");
+    ((int*)p)[0] = realTYPE;
+    ((int*)p)[1] = 0xED0ED;
+  } while(!mps_commit(ap, p, size + headerSIZE));
+
+  return userP;
+}
+
+
+static void *test(void *arg, size_t s)
+{
+  mps_arena_t arena;
+  mps_fmt_t format;
+  mps_root_t exactRoot, ambigRoot;
+  unsigned long objs; size_t i;
+  mps_word_t collections, rampSwitch;
+  mps_alloc_pattern_t ramp = mps_alloc_pattern_ramp();
+  int ramping;
+  mps_ap_t busy_ap;
+  mps_addr_t busy_init;
+
+  arena = (mps_arena_t)arg;
+  (void)s; /* unused */
+
+  die(EnsureHeaderFormat(&format, arena), "fmt_create");
+
+  die(mps_pool_create(&pool, arena, mps_class_amc(), format),
+      "pool_create(amc)");
+
+  die(mps_ap_create(&ap, pool, MPS_RANK_EXACT), "BufferCreate");
+  die(mps_ap_create(&busy_ap, pool, MPS_RANK_EXACT), "BufferCreate");
+
+  for(i=0; i<exactRootsCOUNT; ++i)
+    exactRoots[i] = objNULL;
+  for(i=0; i<ambigRootsCOUNT; ++i)
+    ambigRoots[i] = (mps_addr_t)rnd();
+
+  die(mps_root_create_table_masked(&exactRoot, arena,
+                                   MPS_RANK_EXACT, (mps_rm_t)0,
+                                   &exactRoots[0], exactRootsCOUNT,
+                                   (mps_word_t)1),
+      "root_create_table(exact)");
+  die(mps_root_create_table(&ambigRoot, arena,
+                            MPS_RANK_AMBIG, (mps_rm_t)0,
+                            &ambigRoots[0], ambigRootsCOUNT),
+      "root_create_table(ambig)");
+
+  /* create an ap, and leave it busy */
+  die(mps_reserve(&busy_init, busy_ap, 64), "mps_reserve busy");
+
+  collections = 0;
+  rampSwitch = rampSIZE;
+  mps_ap_alloc_pattern_begin(ap, ramp);
+  mps_ap_alloc_pattern_begin(busy_ap, ramp);
+  ramping = 1;
+  objs = 0;
+  while(collections < collectionsCOUNT) {
+    unsigned long c;
+    size_t r;
+
+    c = mps_collections(arena);
+
+    if(collections != c) {
+      collections = c;
+      printf("\nCollection %lu, %lu objects.\n", c, objs);
+      for(r = 0; r < exactRootsCOUNT; ++r) {
+        if (exactRoots[r] != objNULL)
+          die(HeaderFormatCheck(exactRoots[r]), "wrapper check");
+      }
+      if(collections == rampSwitch) {
+        rampSwitch += rampSIZE;
+        if(ramping) {
+          mps_ap_alloc_pattern_end(ap, ramp);
+          mps_ap_alloc_pattern_end(busy_ap, ramp);
+          /* Every other time, switch back immediately. */
+          if(collections & 1) ramping = 0;
+        }
+        if(!ramping) {
+          mps_ap_alloc_pattern_begin(ap, ramp);
+          mps_ap_alloc_pattern_begin(busy_ap, ramp);
+          ramping = 1;
+        }
+      }
+    }
+
+    r = rnd();
+    if(r & 1) {
+      i = (r >> 1) % exactRootsCOUNT;
+      if(exactRoots[i] != objNULL)
+        die(HeaderFormatCheck(exactRoots[i]), "wrapper check");
+      exactRoots[i] = make();
+      if(exactRoots[(exactRootsCOUNT-1) - i] != objNULL)
+        dylan_write(exactRoots[(exactRootsCOUNT-1) - i],
+                    exactRoots, exactRootsCOUNT);
+    } else {
+      i = (r >> 1) % ambigRootsCOUNT;
+      ambigRoots[(ambigRootsCOUNT-1) - i] = make();
+      /* Create random interior pointers */
+      ambigRoots[i] = (mps_addr_t)((char *)(ambigRoots[i/2]) + 1);
+    }
+
+    if(r % initTestFREQ == 0)
+      *(int*)busy_init = -1; /* check that the buffer is still there */
+
+    if(objs % 1024 == 0) {
+      putchar('.');
+      fflush(stdout);
+    }
+
+    ++objs;
+  }
+
+  (void)mps_commit(busy_ap, busy_init, 64);
+  mps_ap_destroy(busy_ap);
+  mps_ap_destroy(ap);
+  mps_root_destroy(exactRoot);
+  mps_root_destroy(ambigRoot);
+  mps_pool_destroy(pool);
+  mps_fmt_destroy(format);
+
+  return NULL;
+}
+
+
+int main(void)
+{
+  mps_arena_t arena;
+  mps_thr_t thread;
+  void *r;
+
+  die(mps_arena_create(&arena, mps_arena_class_vm(), testArenaSIZE),
+      "arena_create\n");
+  adjust_collection_freq(0.0);
+  die(mps_thread_reg(&thread, arena), "thread_reg");
+  mps_tramp(&r, test, arena, 0);
+  mps_thread_dereg(thread);
+  mps_arena_destroy(arena);
+
+  fflush(stdout); /* synchronize */
+  fprintf(stderr, "\nConclusion:  Failed to find any defects.\n");
+  return 0;
+}