Just my guess...Basically Tbred B low voltage version is made with lower resistence (ohm)material comparing to Tbred B 1.6v normal version.

Lower resistence = lower voltage

Anyway the wattage/power consumption between 1.6v and 1.5v version at the same clock speed will be the same.

Watt = Voltage x Ampere
Although with lower voltage, the current(ampere) required will be higher.
That's why low Vcore version doesn't have significant lower temperature comparing to 1.6v version, at the same clock speed.

Eventually when we add more voltage for it to run at higher clock speed, the temperature will be obviously much higher.

Sorry I am using 56K Modem only..So I cant afford to type Chinese online which will cost me a lot....
Maybe somebody can translate for me.
Thx.