Asus M3N78 Pro: Geforce 8300 & HybridPower Explored

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HYBRID SLI

Hybrid SLI is composed of two different technologies: Geforce Boost and Hybrid Power. Geforce Boost is nVidia's answer to Hybrid Crossfire, which allows an integrated GPU combine forces with a discrete GPU to enhance overall performance. Only two cards are supported so far: the Geforce 8400GS and 8500GT — both entry-level products.

To us, HybridPower is much more compelling. It allows the user to completely turn off the discrete video card in situations where its heavy duty processing power is not required (e.g. idle, watching movies, etc.) which can significantly reduce the power consumption of the system. If implemented correctly, it would deliver the best of both worlds: High performance gaming, and low energy draw. Hybrid Power is supported by the Geforce 9800 and GTX series only.

Asus sent over an ENGTX 260, based on one of the fastest discrete GPPUs produced by nVidia, for us to test the HybridPower feature. nVidia recommended we have at least 2GB of system memory, set the IGP to use at least 256MB of memory, and to connect the video output to the IGP for HybridPower to function properly. These requirements were followed.


HybridPower controls.

Once Hybrid SLI is set up in the BIOS and the latest chipset and graphics drivers are installed, an icon shows up in the system tray, allowing you to switch between Save Power and Performance mode. This had to be done manually, but we expect it will be automated in the future. A third option allows one to use up to four displays — two from the motherboard video and two from the discrete card, but this option doesn't offer any performance or energy saving benefits.


GPU power management, courtesy of Vista.

In Vista the GPU can be automatically set to Save Power mode after the system has been idle for 4 minutes, in case you forget to do so after exiting out of a game.

Test Results - HybridPower

HybridPower Comparison
Test State
System Power Consumption (AC)
Geforce 8300 IGP
Geforce
GTX 260
HybridPower (Save Power)
HybridPower (Performance)
Idle
38W
80W
75W
82W
Rush Hour
47W
97W
86W
98W
Coral Reef
55W
109W
97W
112W
Flight Sim.
62W
123W
108W
126W
Drag Race
66W
124W
107W
126W
CPUBurn
95W
137W
134W
140W
CPUBurn + ATITool
110W
206W
149W
194W
Results were obtained with 2GB of RAM and 256MB assigned to IGP (when applicable). GTX 260 was installed with Forceware 177.41.

First off, it should be noted that the Geforce GTX 260 is very power hungry. Installing it in our test system resulted in the power consumption more than doubling in almost every test state. It's not a surprise that nVidia would target video card power consumption now that some of their cards can use more energy than all the other system components put together. If a powerful, discrete card could be turned off, the power savings would be massive.

Unfortunately, HybridPower doesn't come even close to shutting down the card's power demand entirely. In the Save Power mode, power consumption decreased the most during video playback, 11-17W, but only 5W idle, and only 3W when the CPU was put on load. We did notice the card's cooling fan turning off when Save Power mode was activated, but the card remained fairly warm. It's evident that the card was still drawing a fair amount of power, but not so much that the card would overheat without the fan spinning.

In Performance mode, the IGP being active resulted in a 1-3W increase across the board — fairly insignificant. Strangely when we loaded up CPUBurn and ATITool at the same time, power consumption was lower than just with the discrete card in use. Perhaps HybridPower confused ATITool and it pushed some of the load on the IGP instead — the problem is likely to be with ATITool, which pushes a constant heavy load, rather than the more dynamic up/down load of a typical video game, .



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