AMD HD7970 Graphics Card Review

To test power consumption today we are using a Keithley Integra unit and we measure power consumption from the VGA card inputs, not the system wide drain. We measure results while gaming in Crysis Warhead and record the results.

In such an energy aware climate, AMD are making a big deal out of their new ‘ZeroCore Power' technology. Many solutions today use power gating, clock gating and memory compression to reduce idle power requirements, but ZeroCore power technology can completely power down the core GPU while the rest of the system remains active.

AMD say “Nearly all PCs can be configured to turn off their displays after a long period of inactivity. This is known as the long idle state; where the screen is blanked but the rest of the system remains in an active and working power state (ACPI G0/S0). As soon as the system goes into long idle state and applications are not actively changing the screen contents, the GPU enters the ZeroCore power state. In the ZeroCore power state, the GPU core (including the 3D engine / compute units, multimedia and audio engines, displays, memory interfaces, etc.) is completely powered down.

However, one cannot simply remove the GPU and its associated device context completely; particularly when it is the only GPU in the system as is the case in many enthusiast platforms. The operating system and SBIOS must still be aware that a GPU is still present in the system. For this reason, the ZeroCore Power state maintains a very small bus control block to ensure that GPU context is still visible to the operating system and SBIOS. The ZeroCore power state also manages the power sequencing of the GPU to ensure that the power up/down mechanism is self-contained and independent of the rest of the system.

The enablement of the ZeroCore Power feature is controlled by the driver. The driver monitors the display contents and allows the GPU to enter the ZeroCore Power in the condition that the GPU enters long idle and subsequent work requests are no longer being submitted to the engine. If any applications update the screen contents, ZeroCore Power technology can periodically wake the GPU to update the framebuffer contents and put the GPU back into the ZeroCore Power state. Furthermore, applications such as Windows 7 desktop gadgets are architected to minimize activity and save power in the long idle state. These applications are active during screen-on mode to display dynamic content such as weather, RSS feeds, stock symbols, system status, etc. but also have the intelligence to suspend any updates and activity when the system enters long idle. These applications will not wake the GPU from the ZeroCore Power state in long idle.

AMD ZeroCore Power technology delivers tremendous energy savings. Many PCs remain in the long idle state for a variety of use cases that are highly relevant to everyday consumers, enthusiasts and professionals. In ZeroCore Power mode, users can still enjoy non-graphics activities such as file serving/streaming, motherboard audio and music, and remote access while the GPU core is essentially powered off.”

When in the long idle state, we measured around 4 watts of power drain which is very impressive. Normal idle mode demanded around 13 watts of power. This rose to 221 watts when gaming, and around 270 watts under Furmark load.

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