for people who are taking about HBM. Memory bandwidth isn't that important. The GTX 980 beats R9 290X at 4K though the R9 290X has more bandwidth. and you should know that with 384-bit memory bus interface and 12 GB, the Titan X bandwidth should hit the roof and maybe more tham 4 GB HBM ( memory bandwidth increases with the increase of both of memory capacity and memory bus interface. GTX 970 has 3.5 GB with a 196 GB/s bandwidth and 0.5 GB with a 28 GB/s bandwidth of despite the two parts has a 384-bit memory bus interface and notice that it should a 4 GB with a 228 GB/s bandwidth),but a 12 GB GDDR5 memory will increase power consumption.