The true reputation of a GPU lies in its efficiency. To determine the energy efficiency of a GPU, we need to know both its performance and its power Mic Condenser without Sound Card consumption. Measuring power is relatively simple, but measuring performance is more complex. In this section, we'll look at how to do it properly by pressing the reset button on the GPU's power measurement. There are many different ways to measure power consumption, with varying degrees of difficulty and accuracy. The easiest way is with software like GPU-Z, which tells you what the hardware is reporting. You can also use a power meter like Kill-A-Watt to measure power at the wall socket, but this will only give you an idea of the overall performance of the system, including the inefficiency of the power supply. The best and most accurate way to measure the power consumption of your graphics card is to measure the power consumption between the power supply and the card, but this involves a lot of work. 3D performance requires the most power The power consumption of today's graphics cards has increased significantly. The top models require between 110 and 270 W of power from the PSU. In fact, a powerful graphics card running at full power requires as much power as the rest of the PC's system components combined. If you plan to upgrade to a dual-chip card or expand your system with a second graphics card via SLI or CrossFire, the GPU plays the most important role in determining the wattage your next power supply should deliver. Comparing graphics chips and test configurations When using an overclocked (OC) graphics card, the power consumption will be slightly higher than the specified values. This increase in power consumption should be taken into account when evaluating the power supply's power requirements, and half of the percentage of overclocking can be added to the power consumption as "safe". For example, if your graphics card (GPU) is overclocked by 10%, you need to add 5% to your graphics card's maximum power consumption. If you don't know the clock frequency of your graphics card, you can use the GPU-Z tool to read the value. Test system for power consumption and power bill The 2D value determines the idle power consumption when Windows and the graphics card are idle. This value can be further reduced with current 45 nm CPUs and energy-saving settings. The minimum power consumption of a graphics card is set by the manufacturer. If the GPU and graphics memory do not reduce the clock rate (in the case of the AMD Radeon HD 4870), you can solve this problem yourself by adjusting the clock rate manually with a tool like Riva Tuner or a graphics driver. Otherwise, you will have to put up with the higher power consumption in 2D mode. Power consumption - graphics cards and power costs The power consumption of a graphics card is roughly calculated by subtracting the power consumption of the test system from the total power consumption. The actual values vary depending on the performance class of the 3D graphics chip and are therefore calculated as average values. Please note that we use Nvidia's nForce 780i chipset in SLI with Nvidia graphics cards, which consumes about 50 W more power than Intel's X38 chipset. The GeForce GTX 260 and 280 clearly show the slowness of the new graphics chipsets in 2D mode. The older GeForce 8800 Ultra consumes about twice as much power when running 8 hours per day. The cost of the dual-chip card (Radeon HD 4870 X2) is quite high: if you run the desktop PC continuously for two years, the power bill will reach the purchase price of the card. Power supply efficiency Now that we have a clear picture of the energy costs of graphics cards, we can use this as a basis for a somewhat simplified theory for selecting the power supply class. We need to distinguish between two values: the power measured at the wall socket, which is important for calculating the total power bill, and the actual power load generated by the components. At this stage, it is not possible to guarantee the quality of each power supply manufacturer's products based on the specifications, so some generalizations must be made. The following specifications are for brand name power supplies, but variations in quality are always possible. As always, it is best to avoid cheap power supplies that do not have a proven performance record. For example, if you have a 500-watt power supply and connect components to it that draw 500 watts of power, the power supply is theoretically running at 100% capacity. However, how much power the PSU draws from the outlet and how much heat it dissipates is determined by its efficiency. In this example, if the power supply has an efficiency of 85%, it means that 15% of the power drawn from the outlet is wasted. This means that you are using 500 watts of power, but your electric meter reads 588 watts (since 588 x 85% = 500). This additional power should not be considered when choosing a power supply. It is only relevant for the energy costs. Actual power consumption and power demand Since the power supply's efficiency plays a role and all test measurements are taken at the wall socket, the actual power consumption can be calculated by subtracting the losses due to the power supply's inefficiency. Since the utilization of the graphics cards varies greatly, an average value of 82.4% is used. Unfortunately, another very important factor is now added: the current. At this high value, many older power supplies will fail when a new high-end graphics card is installed. Not all 500W are created equal, especially with cheaper power supplies. Since many components are powered via the 12 V line, the power supply must also have sufficient amperage (A).
For the Radeon HD 4870, for example, AMD states on the packaging that it requires a "500 W power supply". However, according to current measurements, this graphics card does not need more than 150 watts even under full load. If we calculate 150 watts for the CPU, motherboard and drives here, 300 watts should be enough. If we assume a 300 watt load on the 12 V line, this means that we need 25 A on this rail.