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Testing: Our main test test uses the popular software OCCT, which stresses the CPU and the GPU simultaneously, and then graphs the voltages over the period of an hour. Below are the graphs for 3.3V and 12V rails. Our test build did not register with OCCT on the 5V rails:
In the above graph, the green line represents the CPU load, and the brown line represents the actual voltage measurement. In the case of the 3.3V rail, the load drops immediately under load before stabilizing for the remainder of the test. The rail isn't as stable as some, however the lowest value measured 3.2V, and at max measured 3.264V, all well within the defined spec. Interestingly the rail seems to dip briefly and then stabilize at about the 18 minute mark.
The 12V rail was less stable, with a noticeable transition between idle and load. This is largely because the 12V rail is what is responsible for powering both the GPU and the CPU, meaning the load is much more stressful on this rail as opposed to the other rails. The same dip pattern is noticeable here as well. The lowest value measured was 12.121V, while the highest value measured was 12.32V. Because software testing doesn't have the best visibility to the actual voltage measurement coming from the power supply, I like to confirm results with a DMM. To do this, I measure the 12V rail in one of the PCI-e plugs as it is plugged into the video card. I measure at idle when the system is sitting at the desktop, and then again during the OCCT stress test. In both cases the probing is done for several minutes to look for any variation. Here are the results:
As you can see, the DMM confirms what OCCT sees nearly perfectly. The rail idles a bit high but still well within spec. OCCT tends to magnify small voltage variences typical to today's power supplies but it does make a good comparison tool for the stability between different units. Noise and Heat: Despite the vertical installation and my decision to mount the fan facing the case vent, the X4 ran remarkably quiet. It never reached a dB level over the ambient case noise as accented by the rather loud video card fans. During testing the X4 remained consistently at about 36 degrees C as measured through the honeycomb grille and measured by an infrared thermometer. This is about 10 degrees Celsius over room temperature. While this is a bit higher than we have experienced in some units, the X4 remains consistent in its temperature never spiking or ramping the fan excessively. The performance would probably have improved more had the case fans not been set to 60% prior to testing, I just never needed to. Conclusion: With the X4 850 W power supply, Ultra has raised the bar for mid range power supplies. The X4 is loaded with features you usually find in much more expensive units and often over the 1000W mark while keeping the price from climbing to far out of a typical upgrade budget. The decision to go with a single massive +12V rail is an interesting one and may hint at additional models still on the horizon. However the rails remain stable and consistent during testing. Taking into account both Ultra's lifetime warranty and the massive flexibility of the modular design of the rails makes the X4 a solid recommend. There is a lot of competition in the power supply market but the extra cost of a certified 80 Plus power supply can pay for it's self quickly in an enthusiast build. Remember your performance PC is only as good as its weakest link! Don't let your build be based on a weak foundation, get a good high performance power supply like the X4. It's just a good investment.
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