Hi, Setup is as follows. On the RTSM model only. This failure is not repeatable with the builtin sim. /home/ed/images/j2sdk-client-slowdebug/bin/java -version ~/SPECjvm2008$ /home/ed/images/j2sdk-client-slowdebug/bin/java -version openjdk version "1.8.0-internal-debug" OpenJDK Runtime Environment (build 1.8.0-internal-debug-ed_2014_01_07_10_53-b00) OpenJDK 64-Bit Client VM (build 25.0-b59-debug, mixed mode) Command taskset 10 /home/ed/images/j2sdk-client-slowdebug/bin/java -XX:+UseBiasedLocking -jar SPECjvm2008.jar -bt 16 -ikv xml.validation produces the error # Internal Error (/home/ed/work/rc3/jdk8/hotspot/src/share/vm/runtime/synchronizer.cpp:1297), pid=14154, tid=546926752240 # assert(dmw->is_neutral()) failed: invariant The failure does not happen every time, but with taskset 10 and -bt 16 it seems fairly dependable (I have just run it 6 times in a row and it has failed every time). taskset 10 tells it to use a single core (ie. core 5) -bt 16 tells it to run the benchmark as 16 threads. The problem does not seem to occur without the taskset 10, ie. it seems to be running multi threaded single core that provokes it. The problem is more frequent the higher the -bt N value, but making it too high causes out of memory errors. Slowdebug seems to provoke the problem more than fastdebug, although this may just be my perception. All the best, Ed.