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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.
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HybridPower controls.
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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.
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GPU power management, courtesy of Vista.
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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
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HybridPower Comparison
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Test State
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System Power Consumption (AC)
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Geforce 8300 IGP
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Geforce
GTX 260
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HybridPower (Save Power)
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HybridPower (Performance)
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Idle
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38W
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80W
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75W
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82W
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Rush Hour
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47W
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97W
|
86W
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98W
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Coral Reef
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55W
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109W
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97W
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112W
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Flight Sim.
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62W
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123W
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108W
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126W
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Drag Race
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66W
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124W
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107W
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126W
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CPUBurn
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95W
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137W
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134W
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140W
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CPUBurn + ATITool
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110W
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206W
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149W
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194W
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| 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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