Please join the gem5-gpu-dev email list by requesting access here
If you use gem5-gpu in your research, we would appreciate a citation togem5-gpu: A Heterogeneous CPU-GPU Simulator.
gem5-gpu: A Heterogeneous CPU-GPU Simulator Jason Power, Joel Hestness, Marc S. Orr, Mark D. Hill, David A. Wood. Computer Architecture Letters vol. 13, no. 1, Jan 2014 bibtex
There are a number of places to get help using and developing gem5-gpu. Below is an ordered list where you should look for help.