Power Supply - Watt Did You Say?
Power consumption then.
The 7900GT requires a stable 12-volt power source for best performance, reliability and most of all that gaming experience of yours. We've tested a lot of PSU's lately, be sure to read though a couple of reviews.
For a GeForce 7900 GT or GTX graphics card, NVIDIA recommends a 350-400 watt power supply with 22-26 ampere on the 12 volts rails. NVIDIA is recommending nothing too over-the-top in terms of wattage for the power supply unit, yet be aware as that's a lot of Ampage on the 12 volts rails. What we always do with new graphics' cards is we measure the wattage peak with the help of a wattage meter. Slight side note, you are looking at the overall usage of the entire PC.
The meter is placed between the power connector and the PSU. You basically look at how much power is the power circuit in your house pulling from the PSU, so you need to look at the results as being an indication and not an exact science.
Let's have a look at consumption:
Now the table is empty as we moved on towards the more energy efficient Core 2 Duo E6700 processor !
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| Card |
PC Power Consumption in Watt |
| Sparkle GeForce 7900 GT |
200 |
| Sparkle GeForce 7900 GT SLI |
275 | |
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W
e simply look at the peak Wattage during a 3DMark05 session to verify power consumption. You are not looking at the power consumption of the graphics card, but of the entire PC.
So indeed, you need 350w at the least as you want some spare wattage and 420 Watts or better is definitely recommended. When you buy a new PSU you should look at the packaging and check the 12 volt rail's amperage, it should be 22 AMPS minimal (for the total number of +12 volts rails).
If in a later stage or immediately you decide to go for SLI then we need to redo the math. For two 7900 GT's the 420 Watts PSU could still be sufficient. But for the 7900 GT SLI I really recommend a 520 Watt SLI-Ready PSU, preferably with dual 12 volts rails.
There are some good SLI certified PSU's out there, again have a look at our PSU reviews.
What would happen if your PSU can't cope with the load?:
- bad 3D performance
- crashing games
- spontaneous resetting PC
- freezes during gameplay
- PSU overload can cause it to break down
So many things can happen.
Dangerous Liaisons - temperatures of the graphics card
The Calibre series does not have reference coolers as specified by NVIDIA and well .. I'm happy. These coolers are working really well. Let's have a look at the temperatures these design coolers produce. We measured at a room temperature of 23 Degrees C.
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| Card |
Temperature in idle (Celsius) |
Temperature at 100% load in (Celsius) |
| GeForce 7900 GT Sparkle |
42 |
63 |
| GeForce 7900 GT Reference |
45 |
72 | |
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A maximum a 63 Degrees C peak temperature was monitored at the 7900 GT. This is on par and even a little lower compared to the reference cooler with the one difference, this one looks cooler and you can hardly hear it.
Noise Levels coming from the graphics card
When graphics cards produce a lot of heat usually that heat needs to be transported away from the hot core as fast as possible. Often you'll see massive active fan solutions that can indeed get rid of the heat, yet all the fans these days make the PC a noisy son of a gun. I'm doing a little try out today with noise monitoring, so basically the test we do is extremely subjective. We bough a certified dBA meter and will start measuring how many dBA originate from the PC. Why is this subjective you ask? Well, there is always noise in the background, from the streets, from the HD, PSU fan etc etc, so this is by a mile or two not a precise measurement. You could only achieve objective measurement in a sound test chamber.
The human hearing system has different sensitivities at different frequencies. This means that the perception of noise is not at all equal at every frequency. Noise with significant measured levels (in dB) at high or low frequencies will not be as annoying as it would be when its energy is concentrated in the middle frequencies. In other words, the measured noise levels in dB will not reflect the actual human perception of the loudness of the noise. That's why we measure the dBa level. A specific circuit is added to the sound level meter to correct its reading in regard to this concept. This reading is the noise level in dBA. The letter A is added to indicate the correction that was made in the measurement.
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TYPICAL SOUND LEVELS |
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Jet takeoff (200 feet) |
120 dBA |
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Construction Site |
110 dBA |
Intolerable |
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Shout (5 feet) |
100 dBA |
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Heavy truck (50 feet) |
90 dBA |
Very noisy |
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Urban street |
80 dBA |
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Automobile interior |
70 dBA |
Noisy |
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Normal conversation (3 feet) |
60 dBA |
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Office, classroom |
50 dBA |
Moderate |
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Living room |
40 dBA |
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Bedroom at night |
30 dBA |
Quiet |
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Broadcast studio |
20 dBA |
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Rustling leaves |
10 dBA |
Barely audible | |
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We startup a benchmark, we take the dBA meter, move away 75 CM and then aim the device at the active fan on the graphics card.
We measure roughly 41 dBa on the product, which is to be considered a Quiet noise level coming from the PC. Again, this is a very subjective test. I do think that the reference coolers are a tad too noisy so this cooler I simply love.
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