2.2 is the stock vdimm on my ballistix.
The HZs used to be rated for 2.1-2.3v, but now they have been reduced to 2-2.1v......
My HZs arrived today, XP32 is picking up 3.6GB of ram which isn't bad. I will get Vista64 on it soon, and take the HZs for a bit of a clock.