AMD Radeon HD 4770 Review 51

AMD Radeon HD 4770 Review

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Power Consumption

Cooling modern video cards is becoming more and more difficult, especially when users are asking for quiet cooling solutions. That's why the engineers are now paying much more attention to power consumption of new video card designs.

Test System
CPU:Intel Core i7 920 @ 3.8 GHz
(Bloomfield, 8192 KB Cache)
Motherboard:Gigabyte X58 Extreme
Intel X58
Kindly supplied by Gigabyte
Memory:2x 1024MB OCZ DDR3 Platinum @ 1140 MHz 6-6-6-19
Harddisk:WD Raptor 740ADFD 74 GB
Power Supply:BFG ES-800 800W
Software:Windows Vista SP1

In order to characterize a video card's power consumption, the whole system's mains power draw was measured. This means that these numbers include CPU, Memory, HDD, Video card and PSU inefficiency.

The three result values are as following:
  • Idle: Windows sitting at the desktop (1024x768 32-bit) all windows closed, drivers installed.
  • Average: 3DMark03 Nature at 1280x1024, 6xAA, 16xAF. This results in the highest power consumption. Average of all readings (two per second) while the test was rendering (no title screen).
  • Peak: 3DMark03 Nature at 1280x1024, 6xAA, 16xAF. This results in the highest power consumption. Highest single reading
Even though ATI has implemented a 2D/3D clock switching model, the power consumption in idle is still quite high. One reason for that is that only the core frequency is reduced, while memory keeps running at full speed for the whole time. During testing I noticed that any memory frequency change will make the screen display flicker, which is probably the reason why AMD chose not to allow dynamic memory clock changes. I am surprised that AMD has not fixed this problem in their second GDDR5-capable GPU.

In idle the power consumption is not very impressive, I had much higher (in that case lower) hopes for a midrange 40 nm GPU board.

Under load the picture changes dramatically. The HD 4770 is one of the most efficient designs when it comes to performance per Watt. It is only topped by the HD 4830 and the HD 4670. NVIDIA's 9800 GT is trailing behind, far out of sight, with over 20% less performance/Watt.

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