diff --git a/src/readTSC.C b/src/readTSC.C
index 19d3d3a3..7025c08a 100644
--- a/src/readTSC.C
+++ b/src/readTSC.C
@@ -16,13 +16,25 @@
 //
 ///////////////////////////////////////////////////////////////////////////////
 
-long long readTSC(void)
+unsigned long long readTSC(void)
 {
-  union { long long complete; unsigned int part[2]; } ticks;
+  union { unsigned long long complete; unsigned int part[2]; } ticks;
+#ifdef __amd64__
   __asm__ ("rdtsc; mov %%eax,%0;mov %%edx,%1"
             : "=mr" (ticks.part[0]),
               "=mr" (ticks.part[1])
             : /* no inputs */
             : "eax", "edx");
+#elif __powerpc__
+  unsigned int tmp;
+  __asm__ ("0:"
+            "mftbu %[hi32]\n"
+            "mftb %[lo32]\n"
+            "mftbu %[tmp]\n"
+            "cmpw %[tmp],%[hi32]\n"
+            "bne 0b\n"
+            : [hi32] "=r"(ticks.part[0]), [lo32] "=r"(ticks.part[1]),
+            [tmp] "=r"(tmp));
+#endif
   return ticks.complete;
 }