Power Supply - Watt Did You Say?
Power consumption then.
The 7900 GS requires a stable 12-volt power source for best performance, reliability and most of all that gaming experience of yours. We tested a lot of PSU's lately, be sure to read though a couple of reviews.
NVIDIA states that the maximum peak is 82 Watt for the 7900 GS.
So for a GeForce 7900 GS NVIDIA recommends a 300-350 watt power supply with 22-23 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 for a 12 volts rails.
What we always do with new graphics' cards, 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. So please understand that using a Wattage meter is not the most reliable way of measuring power consumption. You basically look at how much power is the power circuit from 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 power consumption:
Now the table is pretty empty as we moved on towards the more energy efficient Core 2 Duo (Conroe) processor !
 |
 |
 |
|
| Card |
PC Power Consumption in Watt |
| GeForce 7900 GS |
187 |
| GeForce 7900 GT |
204 |
| GeForce 7900 GS Galaxy |
232 |
| GeForce 7900 GS SLI |
245 |
| GeForce 7900 GT SLI |
275 | |
|
 |
|
 |
We 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. You'll notice that the Galaxy card uses roughly 230 Watts.
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 then look at the packaging and check the 12 volts rail on Ampere, it should be 22 AMPS minimal (for the total 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 GS's the 420 Watts PSU could still be sufficient.
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
Sure it's a Zalman cooler on that Galaxy card, and we know they are working really well. Let's have a look at the temperatures these coolers produce. We measured at a room temperature of 23 Degrees C.
|
|
|
|
| Card |
Temperature in idle (Celsius) |
Temperature at 100% load in (Celsius) |
| GeForce 7600 GT |
42 |
63 |
| GeForce 7900 GS (Galaxy) |
45 |
61 |
| GeForce 7900 GS (XFX) |
42 |
67 |
| GeForce 7900 GS (Sparkle) |
44 |
66 |
| GeForce 7900 GS (Ref) |
44 |
65 |
| GeForce 7900 GT |
45 |
72 | |
|
|
|
|
A maximum of 61Degrees C peak temperature was monitored at the card. And that's including the default overclock ... nice !
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.
|
|
|
|
|
TYPICAL SOUND LEVELS |
|
Jet takeoff (200 feet) |
120 dBA |
|
|
Construction Site |
110 dBA |
Intolerable |
|
Shout (5 feet) |
100 dBA |
|
|
Heavy truck (50 feet) |
90 dBA |
Very noisy |
|
Urban street |
80 dBA |
|
|
Automobile interior |
70 dBA |
Noisy |
|
Normal conversation (3 feet) |
60 dBA |
|
|
Office, classroom |
50 dBA |
Moderate |
|
Living room |
40 dBA |
|
|
Bedroom at night |
30 dBA |
Quiet |
|
Broadcast studio |
20 dBA |
|
|
Rustling leaves |
10 dBA |
Barely audible | |
|
|
|
|
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.
|
|
|
|
| Card |
Sound Level in measured inDBa |
| GeForce 7900 GS (Galaxy) |
43 |
| GeForce 7900 GS (XFX) |
49 |
| GeForce 7900 GS (Sparkle) |
48 |
| GeForce 7900 GS (NV Ref) |
49 |  |
|
|
|
|
We measure roughly 43-44 dBA on the Zalman edition 7900 GS. That's really good. This test was under full system load which is to be considered a quiet to moderate noise level coming from the entire PC. Again, this is a very subjective test.
Site
Navigation
