The new 27-inch iMac uses up to 365W vs 280W for the old 24-inch! (going by Apple's published max. power consumption numbers. I doubt they would lie because it isn't exactly favourable for them to put in falsely high numbers in an environmental report).
That means there's some extra beef behind the extra components. Perhaps the ATI 4670 is a bit overclocked and the 4850 runs a bit faster than the old iMacs? Admittedly that 2.8 GHz i7 is going to suck a fair bit of power - the recent 2.8 GHz i7 860 model runs at a 95W TDP, however, the quad core iMac isn't available until November. So it won't be using the i7 860, and my guess it is using another custom processor, something a bit more power efficient, somewhere in between the 55W TDP of the old iMacs and the 95W TDP of the i7 860.
The difference between the power consumption of the two computers is 85W. The old iMac had a 24-watt digital amplifier, this new one has two 17-watt amplifiers. That brings the delta down to 75W. Say the iMac's i7 processor has an 80W TDP. That now brings the delta down to 50W. The new display likely wouldn't increase power consumption because of the LED backlight.
I'm not sure if I'm missing much (OK, two extra RAM chips may use another few watts), but there is still a fairly massive 50W unaccounted for.
Just a bit of fat to chew on
That means there's some extra beef behind the extra components. Perhaps the ATI 4670 is a bit overclocked and the 4850 runs a bit faster than the old iMacs? Admittedly that 2.8 GHz i7 is going to suck a fair bit of power - the recent 2.8 GHz i7 860 model runs at a 95W TDP, however, the quad core iMac isn't available until November. So it won't be using the i7 860, and my guess it is using another custom processor, something a bit more power efficient, somewhere in between the 55W TDP of the old iMacs and the 95W TDP of the i7 860.
The difference between the power consumption of the two computers is 85W. The old iMac had a 24-watt digital amplifier, this new one has two 17-watt amplifiers. That brings the delta down to 75W. Say the iMac's i7 processor has an 80W TDP. That now brings the delta down to 50W. The new display likely wouldn't increase power consumption because of the LED backlight.
I'm not sure if I'm missing much (OK, two extra RAM chips may use another few watts), but there is still a fairly massive 50W unaccounted for.
Just a bit of fat to chew on