7900GT draws significantly less power?

[xenolith]

According to anandtech's own review concerning total system power draw here, is it correct for us to conclude that the 7900GT draws 17 watts less power than the 7800GT? If so:

56w (7800GT under load) minus 17w = 39 watts!!! I mean, if they made an AGP version, it practically could run w/o a supplemental power connector.

Is the 110nm to 90nm die shrink the sole reason for such a large power savings?

BTW, while I'm here, does anybody have a theory as to why all middle to mid-upper range PCIe video cards require a robust 6-pin power connector (with two +12v lines) if the standard 16x PCIe slots provide 75 watts? Data extracted from xbitlabs article 1, article 2:

nVidia
7900GT_____||||| 39W?
7800GT_____||||||| 56W
7600GT_____|||| 25W!?
6800ULTRA__||||||||| 72W
6800GT_____||||||| 55W
6800_______||||| 38W
6600GT_____|||||| 47W
6600_______|||| 27W

ATI
X1800XT____|||||||||||| 103W (can see why this needs a power connector)
X1800XL____||||||| 57W
X1600XT____|||| 41W
X850XTPE___||||||||| 74W (very close)
X850XT_____|||||||| 68W
X800PE_____|||||||| 63W
X800PRO____||||| 48W

My theory is, it's probably because it would be too costly for motherboard partners to provide the extra voltage regulation to supply a truely stable load to three or four PCIe slots? [(SLI/x16: 75W * 2) + (x1: 10W) + (x4: 25W?) = 185 watts!) If true, it be interesting to find out how much, or I should say, how little power can be supplied through these slots, depending on the specific motherboard of course.

Edit: added the 7600GT @ 25W!?

 

[firewolfsm]

Nice, now i really can't wait until my 7900GT step-up comes.

 

[1Dark1Sharigan1]

According to guru3D.com, the 7900GTX consumes roughly 120W under load, so that would make the 7800GT load wattage 85W and the 7900GT load wattage 68W . . . which is still <75W

 

[coldpower27]

No I don't think so as the power measurng techniques at Xbitlabs are of different caliber then the ones used here and the results are directly comparable watt to watt wise...

I would guess maybe ~ 54W for 7900 GT based on Xbitlabs measuring methods.
I would guess maybe ~ 80W for 7900 GTX based on Xbitlabs measuring methods.
I would guess maybe ~ 45W for 7600 GT based on Xbitlabs measuring methods.

On this scale though the X1900 XTX looks pretty gas guzzuling with a power draw of 120W, followed by X1900 XT with 108W, followed by X1800 XT with 103W.

 

[coldpower27]

I think anything beyond 50W and you need to add the auxilirary connector to the card for extra power as a precuation. So probably if 2/3 loads is breached you need to be on the safe side and add the extra power connector.

 

[xenolith]

Originally posted by: coldpower27
No I don't think so as the power measurng techniques at Xbitlabs are of different caliber then the ones used here and the results are directly comparable watt to watt wise...

I would guess maybe ~ 54W for 7900 GT based on Xbitlabs measuring methods.
I would guess maybe ~ 80W for 7900 GTX based on Xbitlabs measuring methods.
i would guess maybe ~ 45W for 7600 GT based on Xbitlabs measuring methods.

Good point. Anandtech's method looked at the overall usage of the entire PC with a simple wattage meter placed between the wall outlet and the PSU. While Xbitlabs used "... a special modified mainboard that has special shunts attached to PCI Express x16 power lanes...", which I can imagine are significantly more accurate.

Plus, I'm pretty sure 3Dguru, the inq, et.al. are just quoting nVidia's press release specs of 120w peak power for the 7900GTX; meaningless.

 

[Dethfrumbelo]

ATI's power draw has been increasing while Nvidia's has been decreasing over recent generations.

Higher transistor counts for ATI, which means higher power consumption. Lower transistor counts for Nvidia. Die shrinks for both, which lowers power consumption.

It would be amazing if G80 had even fewer transistors than G71 coupled with a die shrink.

 

[1Dark1Sharigan1]

Originally posted by: xenolith
Plus, I'm pretty sure 3Dguru, the inq, et.al. are just quoting nVidia's press release specs of 120w peak power for the 7900GTX; meaningless.

No they measured it with a watt meter. It was my bad though because because they measured with a watt meter the wattage measured is actually how much the PSU is drawing from the outlet so the measurement needs to be corrected based on the power supply effeciency: http://www.guru3d.com/article/Videocards/326/4/

 

[xenolith]

Originally posted by: 1Dark1Sharigan1

Originally posted by: xenolith
Plus, I'm pretty sure 3Dguru, the inq, et.al. are just quoting nVidia's press release specs of 120w peak power for the 7900GTX; meaningless.

No they measured it with a watt meter. It was my bad though because because they measured with a watt meter the wattage measured is actually how much the PSU is drawing from the outlet so the measurement needs to be corrected based on the power supply effeciency: http://www.guru3d.com/article/Videocards/326/4/

I realize guru3d used a wattage meter, as you acknowledged, with the same method as anandtech. But guru3d never described why they came to the conclusion it was consuming 120W @ peak power in the article (even though its "peak power" would be nearly impossible to ascertain in such a way). Therefore, they're probably just quoting nVidia's spec.