diff --git a/src/core.cpp b/src/core.cpp
index 6f06a44f..eb91e9d2 100644
--- a/src/core.cpp
+++ b/src/core.cpp
@@ -14,13 +14,13 @@
 using namespace Harp;
 using namespace std;
 
-Core::Core(const ArchDef &a, Decoder &d, MemoryUnit &mem) : 
+Core::Core(const ArchDef &a, Decoder &d, MemoryUnit &mem, Word id) : 
   a(a), iDec(d), mem(mem), pc(0), interruptEnable(false), supervisorMode(true),
   activeThreads(1),
   reg(a.getNThds(), vector<Word>(a.getNRegs())),
   pred(a.getNPRegs(), vector<bool>(a.getNPRegs())),
-  shadowReg(), shadowPReg(), interruptEntry(0)
-{ }
+  shadowReg(), shadowPReg(), interruptEntry(0), id(id)
+{ reg[0][0] = (a.getNThds()<<(a.getWordSize()*8 / 2)) | id; }
 
 void Core::step() {
   Size fetchPos(0), decPos, wordSize(a.getWordSize());
diff --git a/src/harptool.cpp b/src/harptool.cpp
index c1564e2c..3aab3a9b 100644
--- a/src/harptool.cpp
+++ b/src/harptool.cpp
@@ -230,7 +230,7 @@ int emu_main(int argc, char **argv) {
   }
 
   MemoryUnit mu(4096, arch.getWordSize());
-  Core core(arch, *dec, mu);
+  Core core(arch, *dec, mu/*, ID in multicore implementations*/);
 
   RamMemDevice mem(imgFileName.c_str(), arch.getWordSize());
   ConsoleMemDevice console(arch.getWordSize(), cout, core);
diff --git a/src/include/core.h b/src/include/core.h
index 728735a5..1e23d206 100644
--- a/src/include/core.h
+++ b/src/include/core.h
@@ -15,7 +15,7 @@
 namespace Harp {
   class Core {
   public:
-    Core(const ArchDef &a, Decoder &d, MemoryUnit &mem);
+    Core(const ArchDef &a, Decoder &d, MemoryUnit &mem, Word id=0);
     void step();
     bool interrupt(Word r0);
     bool running() const { return activeThreads; }
@@ -25,7 +25,7 @@ namespace Harp {
     Decoder &iDec;
     MemoryUnit &mem;
 
-    Word pc, interruptEntry, shadowPc;
+    Word pc, interruptEntry, shadowPc, id;
     Size activeThreads, shadowActiveThreads;
     std::vector<std::vector<Word> > reg;
     std::vector<std::vector<bool> > pred;