diff --git a/mps/code/thw3i6.c b/mps/code/thw3i6.c
new file mode 100644
index 00000000000..86e5f6edc8f
--- /dev/null
+++ b/mps/code/thw3i6.c
@@ -0,0 +1,168 @@
+/* thw3i3.c: WIN32 THREAD MANAGER x86
+ *
+ * $Id$
+ * Copyright (c) 2001 Ravenbrook Limited.  See end of file for license.
+ *
+ * Implements thread stack scanning.  See <design/thread-manager/>.
+ *
+ * This supports the <code/th.h> together with <code/thw3.c>
+ *
+ * .thread.id: The thread id is used to identify the current thread.
+ *
+ *
+ * ASSUMPTIONS
+ *
+ * .error: some major errors are assumed not to happen.
+ *
+ * Other errors are assumed to only happen in certain circumstances.
+ * .error.get-context: GetThreadContext is assumed to succeed unless the
+ * thread has been destroyed.
+ *
+ * .stack.full-descend:  assumes full descending stack.
+ * i.e. stack pointer points to the last allocated location;
+ * stack grows downwards.
+ *
+ * .stack.below-bottom: it's legal for the stack pointer to be at a
+ * higher address than the registered bottom of stack. This might
+ * happen if the stack of another thread doesn't contain any frames
+ * belonging to the client language. In this case, the stack should
+ * not be scanned.
+ *
+ * .stack.align: assume roots on the stack are always word-aligned,
+ * but don't assume that the stack pointer is necessarily
+ * word-aligned at the time of reading the context of another thread.
+ *
+ * .i6: assumes MPS_ARCH_I6
+ * .i6.sp: The sp in the context is Rsp
+ * .i6.context: Rsp is in control context so .context.sp holds
+ * The root registers are Rdi, Rsi, Rbx, Rbp, Rdx, Rcx, Rax, R8 - R15
+ * these are given by CONTEXT_INTEGER, so .context.regroots holds.
+ *
+ * .nt: uses Win32 specific stuff
+ * HANDLE
+ * DWORD
+ * GetCurrentThreadId
+ * CONTEXT
+ * CONTEXT_CONTROL | CONTEXT_INTEGER
+ * GetThreadContext
+ *
+ * .context: ContextFlags determine what is recorded by
+ * GetThreadContext.  This should be set to whichever bits of the
+ * context that need to be recorded.  This should include:
+ * .context.sp: sp assumed to be recorded by CONTEXT_CONTROL.
+ * .context.regroots: assumed to be recorded by CONTEXT_INTEGER.
+ * see winnt.h for description of CONTEXT and ContextFlags.
+ */
+
+#include "mpm.h"
+
+#if !defined(MPS_OS_W3) || !defined(MPS_ARCH_I6) /* .i6 .nt */
+#error "Compiling thw3i6 when MPS_OS_W3 or MPS_ARCH_I6 not defined."
+#endif
+
+#include "thw3.h"
+
+#include "mpswin.h"
+
+SRCID(thw3i6, "$Id$");
+
+
+Res ThreadScan(ScanState ss, Thread thread, void *stackBot)
+{
+  DWORD id;
+  Res res;
+
+  id = GetCurrentThreadId();
+
+  if(id != thread->id) { /* .thread.id */
+    CONTEXT context;
+    BOOL success;
+    Addr *stackBase, *stackLimit, stackPtr;
+
+    /* scan stack and register roots in other threads */
+
+    /* This dumps the relevent registers into the context */
+    /* .context.flags */
+    context.ContextFlags = CONTEXT_CONTROL | CONTEXT_INTEGER;
+    /* .thread.handle.get-context */
+    success = GetThreadContext(thread->handle, &context);
+    if(!success) {
+      /* .error.get-context */
+      /* We assume that the thread must have been destroyed. */
+      /* We ignore the situation by returning immediately. */
+      return ResOK;
+    }
+
+    stackPtr  = (Addr)context.Rsp;   /* .i6.sp */
+    /* .stack.align */
+    stackBase  = (Addr *)AddrAlignUp(stackPtr, sizeof(Addr));
+    stackLimit = (Addr *)stackBot;
+    if (stackBase >= stackLimit)
+      return ResOK;    /* .stack.below-bottom */
+
+    /* scan stack inclusive of current sp and exclusive of
+     * stackBot (.stack.full-descend)
+     */
+    res = TraceScanAreaTagged(ss, stackBase, stackLimit);
+    if(res != ResOK)
+      return res;
+
+    /* (.context.regroots)
+     * This scans the root registers (.context.regroots).  It also
+     * unecessarily scans the rest of the context.  The optimisation
+     * to scan only relevent parts would be machine dependent.
+     */
+    res = TraceScanAreaTagged(ss, (Addr *)&context,
+           (Addr *)((char *)&context + sizeof(CONTEXT)));
+    if(res != ResOK)
+      return res;
+
+  } else { /* scan this thread's stack */
+    res = StackScan(ss, stackBot);
+    if(res != ResOK)
+      return res;
+  }
+
+  return ResOK;
+}
+
+/* C. COPYRIGHT AND LICENSE
+ *
+ * Copyright (C) 2001-2002 Ravenbrook Limited <http://www.ravenbrook.com/>.
+ * All rights reserved.  This is an open source license.  Contact
+ * Ravenbrook for commercial licensing options.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ * 
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 
+ * 3. Redistributions in any form must be accompanied by information on how
+ * to obtain complete source code for this software and any accompanying
+ * software that uses this software.  The source code must either be
+ * included in the distribution or be available for no more than the cost
+ * of distribution plus a nominal fee, and must be freely redistributable
+ * under reasonable conditions.  For an executable file, complete source
+ * code means the source code for all modules it contains. It does not
+ * include source code for modules or files that typically accompany the
+ * major components of the operating system on which the executable file
+ * runs.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+ * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+ * PURPOSE, OR NON-INFRINGEMENT, ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDERS AND CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
diff --git a/mps/code/w3i6mv.nmk b/mps/code/w3i6mv.nmk
index 1ed2fb4eed2..a0c08befd84 100644
--- a/mps/code/w3i6mv.nmk
+++ b/mps/code/w3i6mv.nmk
@@ -22,7 +22,7 @@ MPM = <ring> <mpm> <bt> <protocol> <boot> \
       <root> <format> <buffer> <walk> <lockw3> \
       <ref> <trace> <traceanc> <prmcan> <protw3> \
       <shield> <vmw3> \
-      <than> <ssw3i6> <mpsi> <mpsiw3> <ld> <span> \
+      <thw3> <thw3i6> <ssw3i6> <mpsi> <mpsiw3> <ld> <span> \
       <event> <seg> <sac> <poolmrg> <message> <dbgpool> <dbgpooli> \
       <abq> <meter> <cbs> <poolmv2> <splay> <diag> <version>
 SW  = <ring> <mpm> <bt> <protocol> <boot> \
@@ -31,7 +31,7 @@ SW  = <ring> <mpm> <bt> <protocol> <boot> \
       <root> <format> <buffer> <walk> \
       <ref> <trace> <traceanc> <protsw> <prmcan> \
       <shield> <vmw3> \
-      <thw3i3> <ssan> <mpsi> <ld> \
+      <thw3> <thw3i6> <ssan> <mpsi> <ld> \
       <event> <seg> <sac> <poolmrg> <message> <mpsioan> \
       <poolams> <poolamsi> <dbgpool> <dbgpooli> \
       <abq> <meter> <cbs> <poolmv2> <splay> <diag> <version> <poolmvff>