Battery life and graphic card

I was trying to understand why many recent laptops using Pentium M have
a battery maximum life that is quite short (only a little more than 2
hours).
I thought it might be the dual core Pentium M that uses more power than
the "normal" PM, but then I found a Toshiba spec *** which showed the
same model (Satellite M70) in two different versions, one with a low
cost graphic card (Mobile Intel) and another with a dedicated ATI
Mobility Radeon.
The indicated battery life is 4:32 hours for the first and 2:26 hours
for the second.
They use the same battery, true the second has a slightly faster
processor (2GHz against 1.86 GHz), but is seems to me that the grapchic
card is responsible for the much shorter duration of the battery.

Can anyone confirm this?

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