Beware of VTT - it's a lurking time bomb...

High VTT sends our best QX9650 to an early grave...

We have been using this particular QX960 processor for an upcoming X48 comparison article and testing was going quite well (not blaming a particular board somehow seems appropriate). We thought we had made it past that mystical, magical, and more importantly, stable mark of 450FSB with a Quad Core. However, in order to get to that point on this particular board, we (Editor- Raja in case the police get involved) made the mistake of using a very high VTT termination voltage of 1.51V (VTT is used to terminate data lines between the MCH and CPU).

We should have known better really, especially after Kris posted up a recommended voltage-operating chart in the ASUS Striker II Extreme review.  We do not know what is worse now, Kris saying I told you so (jokingly, well maybe not) or the thought of replacing this $1000 CPU.   We thought it would be beneficial for others to learn from our mistakes so here goes.

This particular CPU was a great example of a QX9650 hitting 4GHz stable at a mere 1.29V on most motherboards (tears are flowing in the beer tonight). We know users are running VTT voltages even higher than ours on 45nm processors and probably have not had a problem yet. We will run high VTT voltages in short bursts to test the limits of the board and CPU. However, this is the first time we have tried anything over 1.45V on a 24+-hour basis to test application stability.

Let this be a warning – do not go over 1.4V maximum for 24/7 use! We are certain that the high VTT voltage and extended testing was the cause of death, as we made no other major or obvious changes within the BIOS that could have instigated a failure. Obviously, we tried to boot the processor in a number of other motherboards without success before we decided to post our results up.

This is our first 45nm Quad core processor we managed to kill outright during testing.  We hope it is the last one too. The problem is that we also have a Q9300 that is on life support after experiencing a 36-hour run at 435FSB with VTT set to 1.45V. While our experiences might not represent results elsewhere, we thought our advice to just, “Say no to high VTT” is worth a quick post.  We have had enough VTT/GTL adjusting in the last year to last us a lifetime – just give us Nehalem quickly, please.